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  • pkg_resources.py 83.53 KiB
    """Package resource API
    --------------------
    
    A resource is a logical file contained within a package, or a logical
    subdirectory thereof.  The package resource API expects resource names
    to have their path parts separated with ``/``, *not* whatever the local
    path separator is.  Do not use os.path operations to manipulate resource
    names being passed into the API.
    
    The package resource API is designed to work with normal filesystem packages,
    .egg files, and unpacked .egg files.  It can also work in a limited way with
    .zip files and with custom PEP 302 loaders that support the ``get_data()``
    method.
    """
    
    import sys, os, zipimport, time, re, imp
    
    try:
        frozenset
    except NameError:
        from sets import ImmutableSet as frozenset
    
    # capture these to bypass sandboxing
    from os import utime, rename, unlink, mkdir
    from os import open as os_open
    from os.path import isdir, split
    
    
    def _bypass_ensure_directory(name, mode=0777):
        # Sandbox-bypassing version of ensure_directory()
        dirname, filename = split(name)
        if dirname and filename and not isdir(dirname):
            _bypass_ensure_directory(dirname)
            mkdir(dirname, mode)
    
    
    
    
    
    
    
    _state_vars = {}
    
    def _declare_state(vartype, **kw):
        g = globals()
        for name, val in kw.iteritems():
            g[name] = val
            _state_vars[name] = vartype
    
    def __getstate__():
        state = {}
        g = globals()
        for k, v in _state_vars.iteritems():
            state[k] = g['_sget_'+v](g[k])
        return state
    
    def __setstate__(state):
        g = globals()
        for k, v in state.iteritems():
            g['_sset_'+_state_vars[k]](k, g[k], v)
        return state
    
    def _sget_dict(val):
        return val.copy()
    
    def _sset_dict(key, ob, state):
        ob.clear()
        ob.update(state)
    
    def _sget_object(val):
        return val.__getstate__()
    
    def _sset_object(key, ob, state):
        ob.__setstate__(state)
    
    _sget_none = _sset_none = lambda *args: None
    
    
    
    
    
    
    def get_supported_platform():
        """Return this platform's maximum compatible version.
    
        distutils.util.get_platform() normally reports the minimum version
        of Mac OS X that would be required to *use* extensions produced by
        distutils.  But what we want when checking compatibility is to know the
        version of Mac OS X that we are *running*.  To allow usage of packages that
        explicitly require a newer version of Mac OS X, we must also know the
        current version of the OS.
    
        If this condition occurs for any other platform with a version in its
        platform strings, this function should be extended accordingly.
        """
        plat = get_build_platform(); m = macosVersionString.match(plat)
        if m is not None and sys.platform == "darwin":
            try:
                plat = 'macosx-%s-%s' % ('.'.join(_macosx_vers()[:2]), m.group(3))
            except ValueError:
                pass    # not Mac OS X
        return plat
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    __all__ = [
        # Basic resource access and distribution/entry point discovery
        'require', 'run_script', 'get_provider',  'get_distribution',
        'load_entry_point', 'get_entry_map', 'get_entry_info', 'iter_entry_points',
        'resource_string', 'resource_stream', 'resource_filename',
        'resource_listdir', 'resource_exists', 'resource_isdir',
    
        # Environmental control
        'declare_namespace', 'working_set', 'add_activation_listener',
        'find_distributions', 'set_extraction_path', 'cleanup_resources',
        'get_default_cache',
    
        # Primary implementation classes
        'Environment', 'WorkingSet', 'ResourceManager',
        'Distribution', 'Requirement', 'EntryPoint',
    
        # Exceptions
        'ResolutionError','VersionConflict','DistributionNotFound','UnknownExtra',
        'ExtractionError',
    
        # Parsing functions and string utilities
        'parse_requirements', 'parse_version', 'safe_name', 'safe_version',
        'get_platform', 'compatible_platforms', 'yield_lines', 'split_sections',
        'safe_extra', 'to_filename',
    
        # filesystem utilities
        'ensure_directory', 'normalize_path',
    
        # Distribution "precedence" constants
        'EGG_DIST', 'BINARY_DIST', 'SOURCE_DIST', 'CHECKOUT_DIST', 'DEVELOP_DIST',
    
        # "Provider" interfaces, implementations, and registration/lookup APIs
        'IMetadataProvider', 'IResourceProvider', 'FileMetadata',
        'PathMetadata', 'EggMetadata', 'EmptyProvider', 'empty_provider',
        'NullProvider', 'EggProvider', 'DefaultProvider', 'ZipProvider',
        'register_finder', 'register_namespace_handler', 'register_loader_type',
        'fixup_namespace_packages', 'get_importer',
    
        # Deprecated/backward compatibility only
        'run_main', 'AvailableDistributions',
    ]
    class ResolutionError(Exception):
        """Abstract base for dependency resolution errors"""
        def __repr__(self): return self.__class__.__name__+repr(self.args)
    
    class VersionConflict(ResolutionError):
        """An already-installed version conflicts with the requested version"""
    
    class DistributionNotFound(ResolutionError):
        """A requested distribution was not found"""
    
    class UnknownExtra(ResolutionError):
        """Distribution doesn't have an "extra feature" of the given name"""
    _provider_factories = {}
    PY_MAJOR = sys.version[:3]
    EGG_DIST    = 3
    BINARY_DIST = 2
    SOURCE_DIST = 1
    CHECKOUT_DIST = 0
    DEVELOP_DIST = -1
    
    def register_loader_type(loader_type, provider_factory):
        """Register `provider_factory` to make providers for `loader_type`
    
        `loader_type` is the type or class of a PEP 302 ``module.__loader__``,
        and `provider_factory` is a function that, passed a *module* object,
        returns an ``IResourceProvider`` for that module.
        """
        _provider_factories[loader_type] = provider_factory
    
    def get_provider(moduleOrReq):
        """Return an IResourceProvider for the named module or requirement"""
        if isinstance(moduleOrReq,Requirement):
            return working_set.find(moduleOrReq) or require(str(moduleOrReq))[0]
        try:
            module = sys.modules[moduleOrReq]
        except KeyError:
            __import__(moduleOrReq)
            module = sys.modules[moduleOrReq]
        loader = getattr(module, '__loader__', None)
        return _find_adapter(_provider_factories, loader)(module)
    
    def _macosx_vers(_cache=[]):
        if not _cache:
            from platform import mac_ver
            _cache.append(mac_ver()[0].split('.'))
        return _cache[0]
    
    def _macosx_arch(machine):
        return {'PowerPC':'ppc', 'Power_Macintosh':'ppc'}.get(machine,machine)
    
    def get_build_platform():
        """Return this platform's string for platform-specific distributions
    
        XXX Currently this is the same as ``distutils.util.get_platform()``, but it
        needs some hacks for Linux and Mac OS X.
        """
        try:
            from distutils.util import get_platform
            plat = get_platform()
        except ImportError:
            import platform
            plat = platform.platform()
        if sys.platform == "darwin" and not plat.startswith('macosx-'):
            try:
                version = _macosx_vers()
                machine = os.uname()[4].replace(" ", "_")
                return "macosx-%d.%d-%s" % (int(version[0]), int(version[1]),
                    _macosx_arch(machine))
            except ValueError:
                # if someone is running a non-Mac darwin system, this will fall
                # through to the default implementation
                pass
        return plat
    
    macosVersionString = re.compile(r"macosx-(\d+)\.(\d+)-(.*)")
    darwinVersionString = re.compile(r"darwin-(\d+)\.(\d+)\.(\d+)-(.*)")
    get_platform = get_build_platform   # XXX backward compat
    
    
    
    
    
    
    
    
    
    def compatible_platforms(provided,required):
        """Can code for the `provided` platform run on the `required` platform?
    
        Returns true if either platform is ``None``, or the platforms are equal.
    
        XXX Needs compatibility checks for Linux and other unixy OSes.
        """
        if provided is None or required is None or provided==required:
            return True     # easy case
    
        # Mac OS X special cases
        reqMac = macosVersionString.match(required)
        if reqMac:
            provMac = macosVersionString.match(provided)
    
            # is this a Mac package?
            if not provMac:
                # this is backwards compatibility for packages built before
                # setuptools 0.6. All packages built after this point will
                # use the new macosx designation.
                provDarwin = darwinVersionString.match(provided)
                if provDarwin:
                    dversion = int(provDarwin.group(1))
                    macosversion = "%s.%s" % (reqMac.group(1), reqMac.group(2))
                    if dversion == 7 and macosversion >= "10.3" or \
                        dversion == 8 and macosversion >= "10.4":
    
                        #import warnings
                        #warnings.warn("Mac eggs should be rebuilt to "
                        #    "use the macosx designation instead of darwin.",
                        #    category=DeprecationWarning)
                        return True
                return False    # egg isn't macosx or legacy darwin
    
            # are they the same major version and machine type?
            if provMac.group(1) != reqMac.group(1) or \
                provMac.group(3) != reqMac.group(3):
                return False
    
    
    
            # is the required OS major update >= the provided one?
            if int(provMac.group(2)) > int(reqMac.group(2)):
                return False
    
            return True
    
        # XXX Linux and other platforms' special cases should go here
        return False
    
    
    def run_script(dist_spec, script_name):
        """Locate distribution `dist_spec` and run its `script_name` script"""
        ns = sys._getframe(1).f_globals
        name = ns['__name__']
        ns.clear()
        ns['__name__'] = name
        require(dist_spec)[0].run_script(script_name, ns)
    
    run_main = run_script   # backward compatibility
    
    def get_distribution(dist):
        """Return a current distribution object for a Requirement or string"""
        if isinstance(dist,basestring): dist = Requirement.parse(dist)
        if isinstance(dist,Requirement): dist = get_provider(dist)
        if not isinstance(dist,Distribution):
            raise TypeError("Expected string, Requirement, or Distribution", dist)
        return dist
    
    def load_entry_point(dist, group, name):
        """Return `name` entry point of `group` for `dist` or raise ImportError"""
        return get_distribution(dist).load_entry_point(group, name)
    
    def get_entry_map(dist, group=None):
        """Return the entry point map for `group`, or the full entry map"""
        return get_distribution(dist).get_entry_map(group)
    
    def get_entry_info(dist, group, name):
        """Return the EntryPoint object for `group`+`name`, or ``None``"""
        return get_distribution(dist).get_entry_info(group, name)
    
    
    class IMetadataProvider:
    
        def has_metadata(name):
            """Does the package's distribution contain the named metadata?"""
    
        def get_metadata(name):
            """The named metadata resource as a string"""
    
        def get_metadata_lines(name):
            """Yield named metadata resource as list of non-blank non-comment lines
    
           Leading and trailing whitespace is stripped from each line, and lines
           with ``#`` as the first non-blank character are omitted."""
    
        def metadata_isdir(name):
            """Is the named metadata a directory?  (like ``os.path.isdir()``)"""
    
        def metadata_listdir(name):
            """List of metadata names in the directory (like ``os.listdir()``)"""
    
        def run_script(script_name, namespace):
            """Execute the named script in the supplied namespace dictionary"""
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    class IResourceProvider(IMetadataProvider):
        """An object that provides access to package resources"""
    
        def get_resource_filename(manager, resource_name):
            """Return a true filesystem path for `resource_name`
    
            `manager` must be an ``IResourceManager``"""
    
        def get_resource_stream(manager, resource_name):
            """Return a readable file-like object for `resource_name`
    
            `manager` must be an ``IResourceManager``"""
    
        def get_resource_string(manager, resource_name):
            """Return a string containing the contents of `resource_name`
    
            `manager` must be an ``IResourceManager``"""
    
        def has_resource(resource_name):
            """Does the package contain the named resource?"""
    
        def resource_isdir(resource_name):
            """Is the named resource a directory?  (like ``os.path.isdir()``)"""
    
        def resource_listdir(resource_name):
            """List of resource names in the directory (like ``os.listdir()``)"""
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    class WorkingSet(object):
        """A collection of active distributions on sys.path (or a similar list)"""
    
        def __init__(self, entries=None):
            """Create working set from list of path entries (default=sys.path)"""
            self.entries = []
            self.entry_keys = {}
            self.by_key = {}
            self.callbacks = []
    
            if entries is None:
                entries = sys.path
    
            for entry in entries:
                self.add_entry(entry)
    
    
        def add_entry(self, entry):
            """Add a path item to ``.entries``, finding any distributions on it
    
            ``find_distributions(entry, True)`` is used to find distributions
            corresponding to the path entry, and they are added.  `entry` is
            always appended to ``.entries``, even if it is already present.
            (This is because ``sys.path`` can contain the same value more than
            once, and the ``.entries`` of the ``sys.path`` WorkingSet should always
            equal ``sys.path``.)
            """
            self.entry_keys.setdefault(entry, [])
            self.entries.append(entry)
            for dist in find_distributions(entry, True):
                self.add(dist, entry, False)
    
    
        def __contains__(self,dist):
            """True if `dist` is the active distribution for its project"""
            return self.by_key.get(dist.key) == dist
    
    
    
    
    
        def find(self, req):
            """Find a distribution matching requirement `req`
    
            If there is an active distribution for the requested project, this
            returns it as long as it meets the version requirement specified by
            `req`.  But, if there is an active distribution for the project and it
            does *not* meet the `req` requirement, ``VersionConflict`` is raised.
            If there is no active distribution for the requested project, ``None``
            is returned.
            """
            dist = self.by_key.get(req.key)
            if dist is not None and dist not in req:
                raise VersionConflict(dist,req)     # XXX add more info
            else:
                return dist
    
        def iter_entry_points(self, group, name=None):
            """Yield entry point objects from `group` matching `name`
    
            If `name` is None, yields all entry points in `group` from all
            distributions in the working set, otherwise only ones matching
            both `group` and `name` are yielded (in distribution order).
            """
            for dist in self:
                entries = dist.get_entry_map(group)
                if name is None:
                    for ep in entries.values():
                        yield ep
                elif name in entries:
                    yield entries[name]
    
        def run_script(self, requires, script_name):
            """Locate distribution for `requires` and run `script_name` script"""
            ns = sys._getframe(1).f_globals
            name = ns['__name__']
            ns.clear()
            ns['__name__'] = name
            self.require(requires)[0].run_script(script_name, ns)
    
    
    
        def __iter__(self):
            """Yield distributions for non-duplicate projects in the working set
    
            The yield order is the order in which the items' path entries were
            added to the working set.
            """
            seen = {}
            for item in self.entries:
                for key in self.entry_keys[item]:
                    if key not in seen:
                        seen[key]=1
                        yield self.by_key[key]
    
        def add(self, dist, entry=None, insert=True):
            """Add `dist` to working set, associated with `entry`
    
            If `entry` is unspecified, it defaults to the ``.location`` of `dist`.
            On exit from this routine, `entry` is added to the end of the working
            set's ``.entries`` (if it wasn't already present).
    
            `dist` is only added to the working set if it's for a project that
            doesn't already have a distribution in the set.  If it's added, any
            callbacks registered with the ``subscribe()`` method will be called.
            """
            if insert:
                dist.insert_on(self.entries, entry)
    
            if entry is None:
                entry = dist.location
            keys = self.entry_keys.setdefault(entry,[])
            keys2 = self.entry_keys.setdefault(dist.location,[])
            if dist.key in self.by_key:
                return      # ignore hidden distros
    
            self.by_key[dist.key] = dist
            if dist.key not in keys:
                keys.append(dist.key)
            if dist.key not in keys2:
                keys2.append(dist.key)
            self._added_new(dist)
    
        def resolve(self, requirements, env=None, installer=None):
            """List all distributions needed to (recursively) meet `requirements`
    
            `requirements` must be a sequence of ``Requirement`` objects.  `env`,
            if supplied, should be an ``Environment`` instance.  If
            not supplied, it defaults to all distributions available within any
            entry or distribution in the working set.  `installer`, if supplied,
            will be invoked with each requirement that cannot be met by an
            already-installed distribution; it should return a ``Distribution`` or
            ``None``.
            """
    
            requirements = list(requirements)[::-1]  # set up the stack
            processed = {}  # set of processed requirements
            best = {}  # key -> dist
            to_activate = []
    
            while requirements:
                req = requirements.pop(0)   # process dependencies breadth-first
                if req in processed:
                    # Ignore cyclic or redundant dependencies
                    continue
                dist = best.get(req.key)
                if dist is None:
                    # Find the best distribution and add it to the map
                    dist = self.by_key.get(req.key)
                    if dist is None:
                        if env is None:
                            env = Environment(self.entries)
                        dist = best[req.key] = env.best_match(req, self, installer)
                        if dist is None:
                            raise DistributionNotFound(req)  # XXX put more info here
                    to_activate.append(dist)
                if dist not in req:
                    # Oops, the "best" so far conflicts with a dependency
                    raise VersionConflict(dist,req) # XXX put more info here
                requirements.extend(dist.requires(req.extras)[::-1])
                processed[req] = True
    
            return to_activate    # return list of distros to activate
    
        def find_plugins(self,
            plugin_env, full_env=None, installer=None, fallback=True
        ):
            """Find all activatable distributions in `plugin_env`
    
            Example usage::
    
                distributions, errors = working_set.find_plugins(
                    Environment(plugin_dirlist)
                )
                map(working_set.add, distributions)  # add plugins+libs to sys.path
                print "Couldn't load", errors        # display errors
    
            The `plugin_env` should be an ``Environment`` instance that contains
            only distributions that are in the project's "plugin directory" or
            directories. The `full_env`, if supplied, should be an ``Environment``
            contains all currently-available distributions.  If `full_env` is not
            supplied, one is created automatically from the ``WorkingSet`` this
            method is called on, which will typically mean that every directory on
            ``sys.path`` will be scanned for distributions.
    
            `installer` is a standard installer callback as used by the
            ``resolve()`` method. The `fallback` flag indicates whether we should
            attempt to resolve older versions of a plugin if the newest version
            cannot be resolved.
    
            This method returns a 2-tuple: (`distributions`, `error_info`), where
            `distributions` is a list of the distributions found in `plugin_env`
            that were loadable, along with any other distributions that are needed
            to resolve their dependencies.  `error_info` is a dictionary mapping
            unloadable plugin distributions to an exception instance describing the
            error that occurred. Usually this will be a ``DistributionNotFound`` or
            ``VersionConflict`` instance.
            """
    
            plugin_projects = list(plugin_env)
            plugin_projects.sort()  # scan project names in alphabetic order
    
            error_info = {}
            distributions = {}
    
            if full_env is None:
                env = Environment(self.entries)
                env += plugin_env
            else:
                env = full_env + plugin_env
    
            shadow_set = self.__class__([])
            map(shadow_set.add, self)   # put all our entries in shadow_set
    
            for project_name in plugin_projects:
    
                for dist in plugin_env[project_name]:
    
                    req = [dist.as_requirement()]
    
                    try:
                        resolvees = shadow_set.resolve(req, env, installer)
    
                    except ResolutionError,v:
                        error_info[dist] = v    # save error info
                        if fallback:
                            continue    # try the next older version of project
                        else:
                            break       # give up on this project, keep going
    
                    else:
                        map(shadow_set.add, resolvees)
                        distributions.update(dict.fromkeys(resolvees))
    
                        # success, no need to try any more versions of this project
                        break
    
            distributions = list(distributions)
            distributions.sort()
    
            return distributions, error_info
    
    
    
    
    
        def require(self, *requirements):
            """Ensure that distributions matching `requirements` are activated
    
            `requirements` must be a string or a (possibly-nested) sequence
            thereof, specifying the distributions and versions required.  The
            return value is a sequence of the distributions that needed to be
            activated to fulfill the requirements; all relevant distributions are
            included, even if they were already activated in this working set.
            """
            needed = self.resolve(parse_requirements(requirements))
    
            for dist in needed:
                self.add(dist)
    
            return needed
    
        def subscribe(self, callback):
            """Invoke `callback` for all distributions (including existing ones)"""
            if callback in self.callbacks:
                return
            self.callbacks.append(callback)
            for dist in self:
                callback(dist)
    
        def _added_new(self, dist):
            for callback in self.callbacks:
                callback(dist)
    
        def __getstate__(self):
            return (
                self.entries[:], self.entry_keys.copy(), self.by_key.copy(),
                self.callbacks[:]
            )
    
        def __setstate__(self, (entries, keys, by_key, callbacks)):
            self.entries = entries[:]
            self.entry_keys = keys.copy()
            self.by_key = by_key.copy()
            self.callbacks = callbacks[:]
    
    
    class Environment(object):
        """Searchable snapshot of distributions on a search path"""
    
        def __init__(self, search_path=None, platform=get_supported_platform(), python=PY_MAJOR):
            """Snapshot distributions available on a search path
    
            Any distributions found on `search_path` are added to the environment.
            `search_path` should be a sequence of ``sys.path`` items.  If not
            supplied, ``sys.path`` is used.
    
            `platform` is an optional string specifying the name of the platform
            that platform-specific distributions must be compatible with.  If
            unspecified, it defaults to the current platform.  `python` is an
            optional string naming the desired version of Python (e.g. ``'2.4'``);
            it defaults to the current version.
    
            You may explicitly set `platform` (and/or `python`) to ``None`` if you
            wish to map *all* distributions, not just those compatible with the
            running platform or Python version.
            """
            self._distmap = {}
            self._cache = {}
            self.platform = platform
            self.python = python
            self.scan(search_path)
    
        def can_add(self, dist):
            """Is distribution `dist` acceptable for this environment?
    
            The distribution must match the platform and python version
            requirements specified when this environment was created, or False
            is returned.
            """
            return (self.python is None or dist.py_version is None
                or dist.py_version==self.python) \
               and compatible_platforms(dist.platform,self.platform)
    
        def remove(self, dist):
            """Remove `dist` from the environment"""
            self._distmap[dist.key].remove(dist)
    
        def scan(self, search_path=None):
            """Scan `search_path` for distributions usable in this environment
    
            Any distributions found are added to the environment.
            `search_path` should be a sequence of ``sys.path`` items.  If not
            supplied, ``sys.path`` is used.  Only distributions conforming to
            the platform/python version defined at initialization are added.
            """
            if search_path is None:
                search_path = sys.path
    
            for item in search_path:
                for dist in find_distributions(item):
                    self.add(dist)
    
        def __getitem__(self,project_name):
            """Return a newest-to-oldest list of distributions for `project_name`
            """
            try:
                return self._cache[project_name]
            except KeyError:
                project_name = project_name.lower()
                if project_name not in self._distmap:
                    return []
    
            if project_name not in self._cache:
                dists = self._cache[project_name] = self._distmap[project_name]
                _sort_dists(dists)
    
            return self._cache[project_name]
    
        def add(self,dist):
            """Add `dist` if we ``can_add()`` it and it isn't already added"""
            if self.can_add(dist) and dist.has_version():
                dists = self._distmap.setdefault(dist.key,[])
                if dist not in dists:
                    dists.append(dist)
                    if dist.key in self._cache:
                        _sort_dists(self._cache[dist.key])
    
    
        def best_match(self, req, working_set, installer=None):
            """Find distribution best matching `req` and usable on `working_set`
    
            This calls the ``find(req)`` method of the `working_set` to see if a
            suitable distribution is already active.  (This may raise
            ``VersionConflict`` if an unsuitable version of the project is already
            active in the specified `working_set`.)  If a suitable distribution
            isn't active, this method returns the newest distribution in the
            environment that meets the ``Requirement`` in `req`.  If no suitable
            distribution is found, and `installer` is supplied, then the result of
            calling the environment's ``obtain(req, installer)`` method will be
            returned.
            """
            dist = working_set.find(req)
            if dist is not None:
                return dist
            for dist in self[req.key]:
                if dist in req:
                    return dist
            return self.obtain(req, installer) # try and download/install
    
        def obtain(self, requirement, installer=None):
            """Obtain a distribution matching `requirement` (e.g. via download)
    
            Obtain a distro that matches requirement (e.g. via download).  In the
            base ``Environment`` class, this routine just returns
            ``installer(requirement)``, unless `installer` is None, in which case
            None is returned instead.  This method is a hook that allows subclasses
            to attempt other ways of obtaining a distribution before falling back
            to the `installer` argument."""
            if installer is not None:
                return installer(requirement)
    
        def __iter__(self):
            """Yield the unique project names of the available distributions"""
            for key in self._distmap.keys():
                if self[key]: yield key
    
    
    
    
        def __iadd__(self, other):
            """In-place addition of a distribution or environment"""
            if isinstance(other,Distribution):
                self.add(other)
            elif isinstance(other,Environment):
                for project in other:
                    for dist in other[project]:
                        self.add(dist)
            else:
                raise TypeError("Can't add %r to environment" % (other,))
            return self
    
        def __add__(self, other):
            """Add an environment or distribution to an environment"""
            new = self.__class__([], platform=None, python=None)
            for env in self, other:
                new += env
            return new
    
    
    AvailableDistributions = Environment    # XXX backward compatibility
    
    
    class ExtractionError(RuntimeError):
        """An error occurred extracting a resource
    
        The following attributes are available from instances of this exception:
    
        manager
            The resource manager that raised this exception
    
        cache_path
            The base directory for resource extraction
    
        original_error
            The exception instance that caused extraction to fail
        """
    
    
    
    
    class ResourceManager:
        """Manage resource extraction and packages"""
        extraction_path = None
    
        def __init__(self):
            self.cached_files = {}
    
        def resource_exists(self, package_or_requirement, resource_name):
            """Does the named resource exist?"""
            return get_provider(package_or_requirement).has_resource(resource_name)
    
        def resource_isdir(self, package_or_requirement, resource_name):
            """Is the named resource an existing directory?"""
            return get_provider(package_or_requirement).resource_isdir(
                resource_name
            )
    
        def resource_filename(self, package_or_requirement, resource_name):
            """Return a true filesystem path for specified resource"""
            return get_provider(package_or_requirement).get_resource_filename(
                self, resource_name
            )
    
        def resource_stream(self, package_or_requirement, resource_name):
            """Return a readable file-like object for specified resource"""
            return get_provider(package_or_requirement).get_resource_stream(
                self, resource_name
            )
    
        def resource_string(self, package_or_requirement, resource_name):
            """Return specified resource as a string"""
            return get_provider(package_or_requirement).get_resource_string(
                self, resource_name
            )
    
        def resource_listdir(self, package_or_requirement, resource_name):
            """List the contents of the named resource directory"""
            return get_provider(package_or_requirement).resource_listdir(
                resource_name
            )
    
        def extraction_error(self):
            """Give an error message for problems extracting file(s)"""
    
            old_exc = sys.exc_info()[1]
            cache_path = self.extraction_path or get_default_cache()
    
            err = ExtractionError("""Can't extract file(s) to egg cache
    
    The following error occurred while trying to extract file(s) to the Python egg
    cache:
    
      %s
    
    The Python egg cache directory is currently set to:
    
      %s
    
    Perhaps your account does not have write access to this directory?  You can
    change the cache directory by setting the PYTHON_EGG_CACHE environment
    variable to point to an accessible directory.
    """         % (old_exc, cache_path)
            )
            err.manager        = self
            err.cache_path     = cache_path
            err.original_error = old_exc
            raise err
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
        def get_cache_path(self, archive_name, names=()):
            """Return absolute location in cache for `archive_name` and `names`
    
            The parent directory of the resulting path will be created if it does
            not already exist.  `archive_name` should be the base filename of the
            enclosing egg (which may not be the name of the enclosing zipfile!),
            including its ".egg" extension.  `names`, if provided, should be a
            sequence of path name parts "under" the egg's extraction location.
    
            This method should only be called by resource providers that need to
            obtain an extraction location, and only for names they intend to
            extract, as it tracks the generated names for possible cleanup later.
            """
            extract_path = self.extraction_path or get_default_cache()
            target_path = os.path.join(extract_path, archive_name+'-tmp', *names)
            try:
                _bypass_ensure_directory(target_path)
            except:
                self.extraction_error()
    
            self.cached_files[target_path] = 1
            return target_path
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
        def postprocess(self, tempname, filename):
            """Perform any platform-specific postprocessing of `tempname`
    
            This is where Mac header rewrites should be done; other platforms don't
            have anything special they should do.
    
            Resource providers should call this method ONLY after successfully
            extracting a compressed resource.  They must NOT call it on resources
            that are already in the filesystem.
    
            `tempname` is the current (temporary) name of the file, and `filename`
            is the name it will be renamed to by the caller after this routine
            returns.
            """
    
            if os.name == 'posix':
                # Make the resource executable
                mode = ((os.stat(tempname).st_mode) | 0555) & 07777
                os.chmod(tempname, mode)
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
        def set_extraction_path(self, path):
            """Set the base path where resources will be extracted to, if needed.
    
            If you do not call this routine before any extractions take place, the
            path defaults to the return value of ``get_default_cache()``.  (Which
            is based on the ``PYTHON_EGG_CACHE`` environment variable, with various
            platform-specific fallbacks.  See that routine's documentation for more
            details.)
    
            Resources are extracted to subdirectories of this path based upon
            information given by the ``IResourceProvider``.  You may set this to a
            temporary directory, but then you must call ``cleanup_resources()`` to
            delete the extracted files when done.  There is no guarantee that
            ``cleanup_resources()`` will be able to remove all extracted files.
    
            (Note: you may not change the extraction path for a given resource
            manager once resources have been extracted, unless you first call
            ``cleanup_resources()``.)
            """
            if self.cached_files:
                raise ValueError(
                    "Can't change extraction path, files already extracted"
                )
    
            self.extraction_path = path
    
        def cleanup_resources(self, force=False):
            """
            Delete all extracted resource files and directories, returning a list
            of the file and directory names that could not be successfully removed.
            This function does not have any concurrency protection, so it should
            generally only be called when the extraction path is a temporary
            directory exclusive to a single process.  This method is not
            automatically called; you must call it explicitly or register it as an
            ``atexit`` function if you wish to ensure cleanup of a temporary
            directory used for extractions.
            """
            # XXX
    
    
    
    def get_default_cache():
        """Determine the default cache location
    
        This returns the ``PYTHON_EGG_CACHE`` environment variable, if set.
        Otherwise, on Windows, it returns a "Python-Eggs" subdirectory of the
        "Application Data" directory.  On all other systems, it's "~/.python-eggs".
        """
        try:
            return os.environ['PYTHON_EGG_CACHE']
        except KeyError:
            pass
    
        if os.name!='nt':
            return os.path.expanduser('~/.python-eggs')
    
        app_data = 'Application Data'   # XXX this may be locale-specific!
        app_homes = [
            (('APPDATA',), None),       # best option, should be locale-safe
            (('USERPROFILE',), app_data),
            (('HOMEDRIVE','HOMEPATH'), app_data),
            (('HOMEPATH',), app_data),
            (('HOME',), None),
            (('WINDIR',), app_data),    # 95/98/ME
        ]
    
        for keys, subdir in app_homes:
            dirname = ''
            for key in keys:
                if key in os.environ:
                    dirname = os.path.join(dirname, os.environ[key])
                else:
                    break
            else:
                if subdir:
                    dirname = os.path.join(dirname,subdir)
                return os.path.join(dirname, 'Python-Eggs')
        else:
            raise RuntimeError(
                "Please set the PYTHON_EGG_CACHE enviroment variable"
            )
    
    def safe_name(name):
        """Convert an arbitrary string to a standard distribution name
    
        Any runs of non-alphanumeric/. characters are replaced with a single '-'.
        """
        return re.sub('[^A-Za-z0-9.]+', '-', name)
    
    
    def safe_version(version):
        """Convert an arbitrary string to a standard version string
    
        Spaces become dots, and all other non-alphanumeric characters become
        dashes, with runs of multiple dashes condensed to a single dash.
        """
        version = version.replace(' ','.')
        return re.sub('[^A-Za-z0-9.]+', '-', version)
    
    
    def safe_extra(extra):
        """Convert an arbitrary string to a standard 'extra' name
    
        Any runs of non-alphanumeric characters are replaced with a single '_',
        and the result is always lowercased.
        """
        return re.sub('[^A-Za-z0-9.]+', '_', extra).lower()
    
    
    def to_filename(name):
        """Convert a project or version name to its filename-escaped form
    
        Any '-' characters are currently replaced with '_'.
        """
        return name.replace('-','_')
    
    
    
    
    
    
    
    
    class NullProvider:
        """Try to implement resources and metadata for arbitrary PEP 302 loaders"""
    
        egg_name = None
        egg_info = None
        loader = None
    
        def __init__(self, module):
            self.loader = getattr(module, '__loader__', None)
            self.module_path = os.path.dirname(getattr(module, '__file__', ''))
    
        def get_resource_filename(self, manager, resource_name):
            return self._fn(self.module_path, resource_name)
    
        def get_resource_stream(self, manager, resource_name):
            return StringIO(self.get_resource_string(manager, resource_name))
    
        def get_resource_string(self, manager, resource_name):
            return self._get(self._fn(self.module_path, resource_name))
    
        def has_resource(self, resource_name):
            return self._has(self._fn(self.module_path, resource_name))
    
        def has_metadata(self, name):
            return self.egg_info and self._has(self._fn(self.egg_info,name))
    
        def get_metadata(self, name):
            if not self.egg_info:
                return ""
            return self._get(self._fn(self.egg_info,name))
    
        def get_metadata_lines(self, name):
            return yield_lines(self.get_metadata(name))
    
        def resource_isdir(self,resource_name):
            return self._isdir(self._fn(self.module_path, resource_name))
    
        def metadata_isdir(self,name):
            return self.egg_info and self._isdir(self._fn(self.egg_info,name))
    
    
        def resource_listdir(self,resource_name):
            return self._listdir(self._fn(self.module_path,resource_name))
    
        def metadata_listdir(self,name):
            if self.egg_info:
                return self._listdir(self._fn(self.egg_info,name))
            return []
    
        def run_script(self,script_name,namespace):
            script = 'scripts/'+script_name
            if not self.has_metadata(script):
                raise ResolutionError("No script named %r" % script_name)
            script_text = self.get_metadata(script).replace('\r\n','\n')
            script_text = script_text.replace('\r','\n')
            script_filename = self._fn(self.egg_info,script)
            namespace['__file__'] = script_filename
            if os.path.exists(script_filename):
                execfile(script_filename, namespace, namespace)
            else:
                from linecache import cache
                cache[script_filename] = (
                    len(script_text), 0, script_text.split('\n'), script_filename
                )
                script_code = compile(script_text,script_filename,'exec')
                exec script_code in namespace, namespace
    
        def _has(self, path):
            raise NotImplementedError(
                "Can't perform this operation for unregistered loader type"
            )
    
        def _isdir(self, path):
            raise NotImplementedError(
                "Can't perform this operation for unregistered loader type"
            )
    
        def _listdir(self, path):
            raise NotImplementedError(
                "Can't perform this operation for unregistered loader type"
            )
    
        def _fn(self, base, resource_name):
            if resource_name:
                return os.path.join(base, *resource_name.split('/'))
            return base
    
        def _get(self, path):
            if hasattr(self.loader, 'get_data'):
                return self.loader.get_data(path)
            raise NotImplementedError(
                "Can't perform this operation for loaders without 'get_data()'"
            )
    
    register_loader_type(object, NullProvider)
    
    
    class EggProvider(NullProvider):
        """Provider based on a virtual filesystem"""
    
        def __init__(self,module):
            NullProvider.__init__(self,module)
            self._setup_prefix()
    
        def _setup_prefix(self):
            # we assume here that our metadata may be nested inside a "basket"
            # of multiple eggs; that's why we use module_path instead of .archive
            path = self.module_path
            old = None
            while path!=old:
                if path.lower().endswith('.egg'):
                    self.egg_name = os.path.basename(path)
                    self.egg_info = os.path.join(path, 'EGG-INFO')
                    self.egg_root = path
                    break
                old = path
                path, base = os.path.split(path)
    
    
    
    
    
    
    class DefaultProvider(EggProvider):
        """Provides access to package resources in the filesystem"""
    
        def _has(self, path):
            return os.path.exists(path)
    
        def _isdir(self,path):
            return os.path.isdir(path)
    
        def _listdir(self,path):
            return os.listdir(path)
    
        def get_resource_stream(self, manager, resource_name):
            return open(self._fn(self.module_path, resource_name), 'rb')
    
        def _get(self, path):
            stream = open(path, 'rb')
            try:
                return stream.read()
            finally:
                stream.close()
    
    register_loader_type(type(None), DefaultProvider)
    
    
    class EmptyProvider(NullProvider):
        """Provider that returns nothing for all requests"""
    
        _isdir = _has = lambda self,path: False
        _get          = lambda self,path: ''
        _listdir      = lambda self,path: []
        module_path   = None
    
        def __init__(self):
            pass
    
    empty_provider = EmptyProvider()
    
    
    
    
    class ZipProvider(EggProvider):
        """Resource support for zips and eggs"""
    
        eagers = None
    
        def __init__(self, module):
            EggProvider.__init__(self,module)
            self.zipinfo = zipimport._zip_directory_cache[self.loader.archive]
            self.zip_pre = self.loader.archive+os.sep
    
        def _zipinfo_name(self, fspath):
            # Convert a virtual filename (full path to file) into a zipfile subpath
            # usable with the zipimport directory cache for our target archive
            if fspath.startswith(self.zip_pre):
                return fspath[len(self.zip_pre):]
            raise AssertionError(
                "%s is not a subpath of %s" % (fspath,self.zip_pre)
            )
    
        def _parts(self,zip_path):
            # Convert a zipfile subpath into an egg-relative path part list
            fspath = self.zip_pre+zip_path  # pseudo-fs path
            if fspath.startswith(self.egg_root+os.sep):
                return fspath[len(self.egg_root)+1:].split(os.sep)
            raise AssertionError(
                "%s is not a subpath of %s" % (fspath,self.egg_root)
            )
    
        def get_resource_filename(self, manager, resource_name):
            if not self.egg_name:
                raise NotImplementedError(
                    "resource_filename() only supported for .egg, not .zip"
                )
            # no need to lock for extraction, since we use temp names
            zip_path = self._resource_to_zip(resource_name)
            eagers = self._get_eager_resources()
            if '/'.join(self._parts(zip_path)) in eagers:
                for name in eagers:
                    self._extract_resource(manager, self._eager_to_zip(name))
            return self._extract_resource(manager, zip_path)
    
        def _extract_resource(self, manager, zip_path):
    
            if zip_path in self._index():
                for name in self._index()[zip_path]:
                    last = self._extract_resource(
                        manager, os.path.join(zip_path, name)
                    )
                return os.path.dirname(last)  # return the extracted directory name
    
            zip_stat = self.zipinfo[zip_path]
            t,d,size = zip_stat[5], zip_stat[6], zip_stat[3]
            date_time = (
                (d>>9)+1980, (d>>5)&0xF, d&0x1F,                      # ymd
                (t&0xFFFF)>>11, (t>>5)&0x3F, (t&0x1F) * 2, 0, 0, -1   # hms, etc.
            )
            timestamp = time.mktime(date_time)
    
            try:
                real_path = manager.get_cache_path(
                    self.egg_name, self._parts(zip_path)
                )
    
                if os.path.isfile(real_path):
                    stat = os.stat(real_path)
                    if stat.st_size==size and stat.st_mtime==timestamp:
                        # size and stamp match, don't bother extracting
                        return real_path
    
                outf, tmpnam = _mkstemp(".$extract", dir=os.path.dirname(real_path))
                os.write(outf, self.loader.get_data(zip_path))
                os.close(outf)
                utime(tmpnam, (timestamp,timestamp))
                manager.postprocess(tmpnam, real_path)
    
                try:
                    rename(tmpnam, real_path)
    
                except os.error:
                    if os.path.isfile(real_path):
                        stat = os.stat(real_path)
    
                        if stat.st_size==size and stat.st_mtime==timestamp:
                            # size and stamp match, somebody did it just ahead of
                            # us, so we're done
                            return real_path
                        elif os.name=='nt':     # Windows, del old file and retry
                            unlink(real_path)
                            rename(tmpnam, real_path)
                            return real_path
                    raise
    
            except os.error:
                manager.extraction_error()  # report a user-friendly error
    
            return real_path
    
        def _get_eager_resources(self):
            if self.eagers is None:
                eagers = []
                for name in ('native_libs.txt', 'eager_resources.txt'):
                    if self.has_metadata(name):
                        eagers.extend(self.get_metadata_lines(name))
                self.eagers = eagers
            return self.eagers
    
        def _index(self):
            try:
                return self._dirindex
            except AttributeError:
                ind = {}
                for path in self.zipinfo:
                    parts = path.split(os.sep)
                    while parts:
                        parent = os.sep.join(parts[:-1])
                        if parent in ind:
                            ind[parent].append(parts[-1])
                            break
                        else:
                            ind[parent] = [parts.pop()]
                self._dirindex = ind
                return ind
    
        def _has(self, fspath):
            zip_path = self._zipinfo_name(fspath)
            return zip_path in self.zipinfo or zip_path in self._index()
    
        def _isdir(self,fspath):
            return self._zipinfo_name(fspath) in self._index()
    
        def _listdir(self,fspath):
            return list(self._index().get(self._zipinfo_name(fspath), ()))
    
        def _eager_to_zip(self,resource_name):
            return self._zipinfo_name(self._fn(self.egg_root,resource_name))
    
        def _resource_to_zip(self,resource_name):
            return self._zipinfo_name(self._fn(self.module_path,resource_name))
    
    register_loader_type(zipimport.zipimporter, ZipProvider)
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    class FileMetadata(EmptyProvider):
        """Metadata handler for standalone PKG-INFO files
    
        Usage::
    
            metadata = FileMetadata("/path/to/PKG-INFO")
    
        This provider rejects all data and metadata requests except for PKG-INFO,
        which is treated as existing, and will be the contents of the file at
        the provided location.
        """
    
        def __init__(self,path):
            self.path = path
    
        def has_metadata(self,name):
            return name=='PKG-INFO'
    
        def get_metadata(self,name):
            if name=='PKG-INFO':
                return open(self.path,'rU').read()
            raise KeyError("No metadata except PKG-INFO is available")
    
        def get_metadata_lines(self,name):
            return yield_lines(self.get_metadata(name))
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    class PathMetadata(DefaultProvider):
        """Metadata provider for egg directories
    
        Usage::
    
            # Development eggs:
    
            egg_info = "/path/to/PackageName.egg-info"
            base_dir = os.path.dirname(egg_info)
            metadata = PathMetadata(base_dir, egg_info)
            dist_name = os.path.splitext(os.path.basename(egg_info))[0]
            dist = Distribution(basedir,project_name=dist_name,metadata=metadata)
    
            # Unpacked egg directories:
    
            egg_path = "/path/to/PackageName-ver-pyver-etc.egg"
            metadata = PathMetadata(egg_path, os.path.join(egg_path,'EGG-INFO'))
            dist = Distribution.from_filename(egg_path, metadata=metadata)
        """
    
        def __init__(self, path, egg_info):
            self.module_path = path
            self.egg_info = egg_info
    
    
    class EggMetadata(ZipProvider):
        """Metadata provider for .egg files"""
    
        def __init__(self, importer):
            """Create a metadata provider from a zipimporter"""
    
            self.zipinfo = zipimport._zip_directory_cache[importer.archive]
            self.zip_pre = importer.archive+os.sep
            self.loader = importer
            if importer.prefix:
                self.module_path = os.path.join(importer.archive, importer.prefix)
            else:
                self.module_path = importer.archive
            self._setup_prefix()
    
    
    class ImpWrapper:
        """PEP 302 Importer that wraps Python's "normal" import algorithm"""
    
        def __init__(self, path=None):
            self.path = path
    
        def find_module(self, fullname, path=None):
            subname = fullname.split(".")[-1]
            if subname != fullname and self.path is None:
                return None
            if self.path is None:
                path = None
            else:
                path = [self.path]
            try:
                file, filename, etc = imp.find_module(subname, path)
            except ImportError:
                return None
            return ImpLoader(file, filename, etc)
    
    
    class ImpLoader:
        """PEP 302 Loader that wraps Python's "normal" import algorithm"""
    
        def __init__(self, file, filename, etc):
            self.file = file
            self.filename = filename
            self.etc = etc
    
        def load_module(self, fullname):
            try:
                mod = imp.load_module(fullname, self.file, self.filename, self.etc)
            finally:
                if self.file: self.file.close()
            # Note: we don't set __loader__ because we want the module to look
            # normal; i.e. this is just a wrapper for standard import machinery
            return mod
    
    
    
    
    def get_importer(path_item):
        """Retrieve a PEP 302 "importer" for the given path item
    
        If there is no importer, this returns a wrapper around the builtin import
        machinery.  The returned importer is only cached if it was created by a
        path hook.
        """
        try:
            importer = sys.path_importer_cache[path_item]
        except KeyError:
            for hook in sys.path_hooks:
                try:
                    importer = hook(path_item)
                except ImportError:
                    pass
                else:
                    break
            else:
                importer = None
    
        sys.path_importer_cache.setdefault(path_item,importer)
        if importer is None:
            try:
                importer = ImpWrapper(path_item)
            except ImportError:
                pass
        return importer
    
    try:
        from pkgutil import get_importer, ImpImporter
    except ImportError:
        pass    # Python 2.3 or 2.4, use our own implementation
    else:
        ImpWrapper = ImpImporter    # Python 2.5, use pkgutil's implementation
        del ImpLoader, ImpImporter
    
    
    
    
    
    
    _declare_state('dict', _distribution_finders = {})
    
    def register_finder(importer_type, distribution_finder):
        """Register `distribution_finder` to find distributions in sys.path items
    
        `importer_type` is the type or class of a PEP 302 "Importer" (sys.path item
        handler), and `distribution_finder` is a callable that, passed a path
        item and the importer instance, yields ``Distribution`` instances found on
        that path item.  See ``pkg_resources.find_on_path`` for an example."""
        _distribution_finders[importer_type] = distribution_finder
    
    
    def find_distributions(path_item, only=False):
        """Yield distributions accessible via `path_item`"""
        importer = get_importer(path_item)
        finder = _find_adapter(_distribution_finders, importer)
        return finder(importer, path_item, only)
    
    def find_in_zip(importer, path_item, only=False):
        metadata = EggMetadata(importer)
        if metadata.has_metadata('PKG-INFO'):
            yield Distribution.from_filename(path_item, metadata=metadata)
        if only:
            return  # don't yield nested distros
        for subitem in metadata.resource_listdir('/'):
            if subitem.endswith('.egg'):
                subpath = os.path.join(path_item, subitem)
                for dist in find_in_zip(zipimport.zipimporter(subpath), subpath):
                    yield dist
    
    register_finder(zipimport.zipimporter, find_in_zip)
    
    def StringIO(*args, **kw):
        """Thunk to load the real StringIO on demand"""
        global StringIO
        try:
            from cStringIO import StringIO
        except ImportError:
            from StringIO import StringIO
        return StringIO(*args,**kw)
    
    def find_nothing(importer, path_item, only=False):
        return ()
    register_finder(object,find_nothing)
    
    def find_on_path(importer, path_item, only=False):
        """Yield distributions accessible on a sys.path directory"""
        path_item = _normalize_cached(path_item)
    
        if os.path.isdir(path_item) and os.access(path_item, os.R_OK):
            if path_item.lower().endswith('.egg'):
                # unpacked egg
                yield Distribution.from_filename(
                    path_item, metadata=PathMetadata(
                        path_item, os.path.join(path_item,'EGG-INFO')
                    )
                )
            else:
                # scan for .egg and .egg-info in directory
                for entry in os.listdir(path_item):
                    lower = entry.lower()
                    if lower.endswith('.egg-info'):
                        fullpath = os.path.join(path_item, entry)
                        if os.path.isdir(fullpath):
                            # egg-info directory, allow getting metadata
                            metadata = PathMetadata(path_item, fullpath)
                        else:
                            metadata = FileMetadata(fullpath)
                        yield Distribution.from_location(
                            path_item,entry,metadata,precedence=DEVELOP_DIST
                        )
                    elif not only and lower.endswith('.egg'):
                        for dist in find_distributions(os.path.join(path_item, entry)):
                            yield dist
                    elif not only and lower.endswith('.egg-link'):
                        for line in file(os.path.join(path_item, entry)):
                            if not line.strip(): continue
                            for item in find_distributions(os.path.join(path_item,line.rstrip())):
                                yield item
                            break
    register_finder(ImpWrapper,find_on_path)
    
    _declare_state('dict', _namespace_handlers = {})
    _declare_state('dict', _namespace_packages = {})
    
    def register_namespace_handler(importer_type, namespace_handler):
        """Register `namespace_handler` to declare namespace packages
    
        `importer_type` is the type or class of a PEP 302 "Importer" (sys.path item
        handler), and `namespace_handler` is a callable like this::
    
            def namespace_handler(importer,path_entry,moduleName,module):
                # return a path_entry to use for child packages
    
        Namespace handlers are only called if the importer object has already
        agreed that it can handle the relevant path item, and they should only
        return a subpath if the module __path__ does not already contain an
        equivalent subpath.  For an example namespace handler, see
        ``pkg_resources.file_ns_handler``.
        """
        _namespace_handlers[importer_type] = namespace_handler
    
    def _handle_ns(packageName, path_item):
        """Ensure that named package includes a subpath of path_item (if needed)"""
        importer = get_importer(path_item)
        if importer is None:
            return None
        loader = importer.find_module(packageName)
        if loader is None:
            return None
        module = sys.modules.get(packageName)
        if module is None:
            module = sys.modules[packageName] = imp.new_module(packageName)
            module.__path__ = []; _set_parent_ns(packageName)
        elif not hasattr(module,'__path__'):
            raise TypeError("Not a package:", packageName)
        handler = _find_adapter(_namespace_handlers, importer)
        subpath = handler(importer,path_item,packageName,module)
        if subpath is not None:
            path = module.__path__; path.append(subpath)
            loader.load_module(packageName); module.__path__ = path
        return subpath
    
    def declare_namespace(packageName):
        """Declare that package 'packageName' is a namespace package"""
    
        imp.acquire_lock()
        try:
            if packageName in _namespace_packages:
                return
    
            path, parent = sys.path, None
            if '.' in packageName:
                parent = '.'.join(packageName.split('.')[:-1])
                declare_namespace(parent)
                __import__(parent)
                try:
                    path = sys.modules[parent].__path__
                except AttributeError:
                    raise TypeError("Not a package:", parent)
    
            # Track what packages are namespaces, so when new path items are added,
            # they can be updated
            _namespace_packages.setdefault(parent,[]).append(packageName)
            _namespace_packages.setdefault(packageName,[])
    
            for path_item in path:
                # Ensure all the parent's path items are reflected in the child,
                # if they apply
                _handle_ns(packageName, path_item)
    
        finally:
            imp.release_lock()
    
    def fixup_namespace_packages(path_item, parent=None):
        """Ensure that previously-declared namespace packages include path_item"""
        imp.acquire_lock()
        try:
            for package in _namespace_packages.get(parent,()):
                subpath = _handle_ns(package, path_item)
                if subpath: fixup_namespace_packages(subpath,package)
        finally:
            imp.release_lock()
    
    def file_ns_handler(importer, path_item, packageName, module):
        """Compute an ns-package subpath for a filesystem or zipfile importer"""
    
        subpath = os.path.join(path_item, packageName.split('.')[-1])
        normalized = _normalize_cached(subpath)
        for item in module.__path__:
            if _normalize_cached(item)==normalized:
                break
        else:
            # Only return the path if it's not already there
            return subpath
    
    register_namespace_handler(ImpWrapper,file_ns_handler)
    register_namespace_handler(zipimport.zipimporter,file_ns_handler)
    
    
    def null_ns_handler(importer, path_item, packageName, module):
        return None
    
    register_namespace_handler(object,null_ns_handler)
    
    
    def normalize_path(filename):
        """Normalize a file/dir name for comparison purposes"""
        return os.path.normcase(os.path.realpath(filename))
    
    def _normalize_cached(filename,_cache={}):
        try:
            return _cache[filename]
        except KeyError:
            _cache[filename] = result = normalize_path(filename)
            return result
    
    def _set_parent_ns(packageName):
        parts = packageName.split('.')
        name = parts.pop()
        if parts:
            parent = '.'.join(parts)
            setattr(sys.modules[parent], name, sys.modules[packageName])
    
    
    def yield_lines(strs):
        """Yield non-empty/non-comment lines of a ``basestring`` or sequence"""
        if isinstance(strs,basestring):
            for s in strs.splitlines():
                s = s.strip()
                if s and not s.startswith('#'):     # skip blank lines/comments
                    yield s
        else:
            for ss in strs:
                for s in yield_lines(ss):
                    yield s
    
    LINE_END = re.compile(r"\s*(#.*)?$").match         # whitespace and comment
    CONTINUE = re.compile(r"\s*\\\s*(#.*)?$").match    # line continuation
    DISTRO   = re.compile(r"\s*((\w|[-.])+)").match    # Distribution or extra
    VERSION  = re.compile(r"\s*(<=?|>=?|==|!=)\s*((\w|[-.])+)").match  # ver. info
    COMMA    = re.compile(r"\s*,").match               # comma between items
    OBRACKET = re.compile(r"\s*\[").match
    CBRACKET = re.compile(r"\s*\]").match
    MODULE   = re.compile(r"\w+(\.\w+)*$").match
    EGG_NAME = re.compile(
        r"(?P<name>[^-]+)"
        r"( -(?P<ver>[^-]+) (-py(?P<pyver>[^-]+) (-(?P<plat>.+))? )? )?",
        re.VERBOSE | re.IGNORECASE
    ).match
    
    component_re = re.compile(r'(\d+ | [a-z]+ | \.| -)', re.VERBOSE)
    replace = {'pre':'c', 'preview':'c','-':'final-','rc':'c','dev':'@'}.get
    
    def _parse_version_parts(s):
        for part in component_re.split(s):
            part = replace(part,part)
            if not part or part=='.':
                continue
            if part[:1] in '0123456789':
                yield part.zfill(8)    # pad for numeric comparison
            else:
                yield '*'+part
    
        yield '*final'  # ensure that alpha/beta/candidate are before final
    
    def parse_version(s):
        """Convert a version string to a chronologically-sortable key
    
        This is a rough cross between distutils' StrictVersion and LooseVersion;
        if you give it versions that would work with StrictVersion, then it behaves
        the same; otherwise it acts like a slightly-smarter LooseVersion. It is
        *possible* to create pathological version coding schemes that will fool
        this parser, but they should be very rare in practice.
    
        The returned value will be a tuple of strings.  Numeric portions of the
        version are padded to 8 digits so they will compare numerically, but
        without relying on how numbers compare relative to strings.  Dots are
        dropped, but dashes are retained.  Trailing zeros between alpha segments
        or dashes are suppressed, so that e.g. "2.4.0" is considered the same as
        "2.4". Alphanumeric parts are lower-cased.
    
        The algorithm assumes that strings like "-" and any alpha string that
        alphabetically follows "final"  represents a "patch level".  So, "2.4-1"
        is assumed to be a branch or patch of "2.4", and therefore "2.4.1" is
        considered newer than "2.4-1", which in turn is newer than "2.4".
    
        Strings like "a", "b", "c", "alpha", "beta", "candidate" and so on (that
        come before "final" alphabetically) are assumed to be pre-release versions,
        so that the version "2.4" is considered newer than "2.4a1".
    
        Finally, to handle miscellaneous cases, the strings "pre", "preview", and
        "rc" are treated as if they were "c", i.e. as though they were release
        candidates, and therefore are not as new as a version string that does not
        contain them, and "dev" is replaced with an '@' so that it sorts lower than
        than any other pre-release tag.
        """
        parts = []
        for part in _parse_version_parts(s.lower()):
            if part.startswith('*'):
                if part<'*final':   # remove '-' before a prerelease tag
                    while parts and parts[-1]=='*final-': parts.pop()
                # remove trailing zeros from each series of numeric parts
                while parts and parts[-1]=='00000000':
                    parts.pop()
            parts.append(part)
        return tuple(parts)
    
    class EntryPoint(object):
        """Object representing an advertised importable object"""
    
        def __init__(self, name, module_name, attrs=(), extras=(), dist=None):
            if not MODULE(module_name):
                raise ValueError("Invalid module name", module_name)
            self.name = name
            self.module_name = module_name
            self.attrs = tuple(attrs)
            self.extras = Requirement.parse(("x[%s]" % ','.join(extras))).extras
            self.dist = dist
    
        def __str__(self):
            s = "%s = %s" % (self.name, self.module_name)
            if self.attrs:
                s += ':' + '.'.join(self.attrs)
            if self.extras:
                s += ' [%s]' % ','.join(self.extras)
            return s
    
        def __repr__(self):
            return "EntryPoint.parse(%r)" % str(self)
    
        def load(self, require=True, env=None, installer=None):
            if require: self.require(env, installer)
            entry = __import__(self.module_name, globals(),globals(), ['__name__'])
            for attr in self.attrs:
                try:
                    entry = getattr(entry,attr)
                except AttributeError:
                    raise ImportError("%r has no %r attribute" % (entry,attr))
            return entry
    
        def require(self, env=None, installer=None):
            if self.extras and not self.dist:
                raise UnknownExtra("Can't require() without a distribution", self)
            map(working_set.add,
                working_set.resolve(self.dist.requires(self.extras),env,installer))
    
    
    
        #@classmethod
        def parse(cls, src, dist=None):
            """Parse a single entry point from string `src`
    
            Entry point syntax follows the form::
    
                name = some.module:some.attr [extra1,extra2]
    
            The entry name and module name are required, but the ``:attrs`` and
            ``[extras]`` parts are optional
            """
            try:
                attrs = extras = ()
                name,value = src.split('=',1)
                if '[' in value:
                    value,extras = value.split('[',1)
                    req = Requirement.parse("x["+extras)
                    if req.specs: raise ValueError
                    extras = req.extras
                if ':' in value:
                    value,attrs = value.split(':',1)
                    if not MODULE(attrs.rstrip()):
                        raise ValueError
                    attrs = attrs.rstrip().split('.')
            except ValueError:
                raise ValueError(
                    "EntryPoint must be in 'name=module:attrs [extras]' format",
                    src
                )
            else:
                return cls(name.strip(), value.strip(), attrs, extras, dist)
    
        parse = classmethod(parse)
    
    
    
    
    
    
    
    
        #@classmethod
        def parse_group(cls, group, lines, dist=None):
            """Parse an entry point group"""
            if not MODULE(group):
                raise ValueError("Invalid group name", group)
            this = {}
            for line in yield_lines(lines):
                ep = cls.parse(line, dist)
                if ep.name in this:
                    raise ValueError("Duplicate entry point", group, ep.name)
                this[ep.name]=ep
            return this
    
        parse_group = classmethod(parse_group)
    
        #@classmethod
        def parse_map(cls, data, dist=None):
            """Parse a map of entry point groups"""
            if isinstance(data,dict):
                data = data.items()
            else:
                data = split_sections(data)
            maps = {}
            for group, lines in data:
                if group is None:
                    if not lines:
                        continue
                    raise ValueError("Entry points must be listed in groups")
                group = group.strip()
                if group in maps:
                    raise ValueError("Duplicate group name", group)
                maps[group] = cls.parse_group(group, lines, dist)
            return maps
    
        parse_map = classmethod(parse_map)
    
    
    
    
    
    
    class Distribution(object):
        """Wrap an actual or potential sys.path entry w/metadata"""
        def __init__(self,
            location=None, metadata=None, project_name=None, version=None,
            py_version=PY_MAJOR, platform=None, precedence = EGG_DIST
        ):
            self.project_name = safe_name(project_name or 'Unknown')
            if version is not None:
                self._version = safe_version(version)
            self.py_version = py_version
            self.platform = platform
            self.location = location
            self.precedence = precedence
            self._provider = metadata or empty_provider
    
        #@classmethod
        def from_location(cls,location,basename,metadata=None,**kw):
            project_name, version, py_version, platform = [None]*4
            basename, ext = os.path.splitext(basename)
            if ext.lower() in (".egg",".egg-info"):
                match = EGG_NAME(basename)
                if match:
                    project_name, version, py_version, platform = match.group(
                        'name','ver','pyver','plat'
                    )
            return cls(
                location, metadata, project_name=project_name, version=version,
                py_version=py_version, platform=platform, **kw
            )
        from_location = classmethod(from_location)
    
        hashcmp = property(
            lambda self: (
                getattr(self,'parsed_version',()), self.precedence, self.key,
                -len(self.location or ''), self.location, self.py_version,
                self.platform
            )
        )
        def __cmp__(self, other): return cmp(self.hashcmp, other)
        def __hash__(self): return hash(self.hashcmp)
    
        # These properties have to be lazy so that we don't have to load any
        # metadata until/unless it's actually needed.  (i.e., some distributions
        # may not know their name or version without loading PKG-INFO)
    
        #@property
        def key(self):
            try:
                return self._key
            except AttributeError:
                self._key = key = self.project_name.lower()
                return key
        key = property(key)
    
        #@property
        def parsed_version(self):
            try:
                return self._parsed_version
            except AttributeError:
                self._parsed_version = pv = parse_version(self.version)
                return pv
    
        parsed_version = property(parsed_version)
    
        #@property
        def version(self):
            try:
                return self._version
            except AttributeError:
                for line in self._get_metadata('PKG-INFO'):
                    if line.lower().startswith('version:'):
                        self._version = safe_version(line.split(':',1)[1].strip())
                        return self._version
                else:
                    raise ValueError(
                        "Missing 'Version:' header and/or PKG-INFO file", self
                    )
        version = property(version)
    
    
    
    
        #@property
        def _dep_map(self):
            try:
                return self.__dep_map
            except AttributeError:
                dm = self.__dep_map = {None: []}
                for name in 'requires.txt', 'depends.txt':
                    for extra,reqs in split_sections(self._get_metadata(name)):
                        if extra: extra = safe_extra(extra)
                        dm.setdefault(extra,[]).extend(parse_requirements(reqs))
                return dm
        _dep_map = property(_dep_map)
    
        def requires(self,extras=()):
            """List of Requirements needed for this distro if `extras` are used"""
            dm = self._dep_map
            deps = []
            deps.extend(dm.get(None,()))
            for ext in extras:
                try:
                    deps.extend(dm[safe_extra(ext)])
                except KeyError:
                    raise UnknownExtra(
                        "%s has no such extra feature %r" % (self, ext)
                    )
            return deps
    
        def _get_metadata(self,name):
            if self.has_metadata(name):
                for line in self.get_metadata_lines(name):
                    yield line
    
        def activate(self,path=None):
            """Ensure distribution is importable on `path` (default=sys.path)"""
            if path is None: path = sys.path
            self.insert_on(path)
            if path is sys.path:
                fixup_namespace_packages(self.location)
                map(declare_namespace, self._get_metadata('namespace_packages.txt'))
    
    
        def egg_name(self):
            """Return what this distribution's standard .egg filename should be"""
            filename = "%s-%s-py%s" % (
                to_filename(self.project_name), to_filename(self.version),
                self.py_version or PY_MAJOR
            )
    
            if self.platform:
                filename += '-'+self.platform
            return filename
    
        def __repr__(self):
            if self.location:
                return "%s (%s)" % (self,self.location)
            else:
                return str(self)
    
        def __str__(self):
            try: version = getattr(self,'version',None)
            except ValueError: version = None
            version = version or "[unknown version]"
            return "%s %s" % (self.project_name,version)
    
        def __getattr__(self,attr):
            """Delegate all unrecognized public attributes to .metadata provider"""
            if attr.startswith('_'):
                raise AttributeError,attr
            return getattr(self._provider, attr)
    
        #@classmethod
        def from_filename(cls,filename,metadata=None, **kw):
            return cls.from_location(
                _normalize_cached(filename), os.path.basename(filename), metadata,
                **kw
            )
        from_filename = classmethod(from_filename)
    
        def as_requirement(self):
            """Return a ``Requirement`` that matches this distribution exactly"""
            return Requirement.parse('%s==%s' % (self.project_name, self.version))
    
        def load_entry_point(self, group, name):
            """Return the `name` entry point of `group` or raise ImportError"""
            ep = self.get_entry_info(group,name)
            if ep is None:
                raise ImportError("Entry point %r not found" % ((group,name),))
            return ep.load()
    
        def get_entry_map(self, group=None):
            """Return the entry point map for `group`, or the full entry map"""
            try:
                ep_map = self._ep_map
            except AttributeError:
                ep_map = self._ep_map = EntryPoint.parse_map(
                    self._get_metadata('entry_points.txt'), self
                )
            if group is not None:
                return ep_map.get(group,{})
            return ep_map
    
        def get_entry_info(self, group, name):
            """Return the EntryPoint object for `group`+`name`, or ``None``"""
            return self.get_entry_map(group).get(name)
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
        def insert_on(self, path, loc = None):
            """Insert self.location in path before its nearest parent directory"""
    
            loc = loc or self.location
            if not loc:
                return
    
            nloc = _normalize_cached(loc)
            bdir = os.path.dirname(nloc)
            npath= [(p and _normalize_cached(p) or p) for p in path]
    
            bp = None
            for p, item in enumerate(npath):
                if item==nloc:
                    break
                elif item==bdir and self.precedence==EGG_DIST:
                    # if it's an .egg, give it precedence over its directory
                    if path is sys.path:
                        self.check_version_conflict()
                    path.insert(p, loc)
                    npath.insert(p, nloc)
                    break
            else:
                if path is sys.path:
                    self.check_version_conflict()
                path.append(loc)
                return
    
            # p is the spot where we found or inserted loc; now remove duplicates
            while 1:
                try:
                    np = npath.index(nloc, p+1)
                except ValueError:
                    break
                else:
                    del npath[np], path[np]
                    p = np  # ha!
    
            return
    
    
        def check_version_conflict(self):
            if self.key=='setuptools':
                return      # ignore the inevitable setuptools self-conflicts  :(
    
            nsp = dict.fromkeys(self._get_metadata('namespace_packages.txt'))
            loc = normalize_path(self.location)
            for modname in self._get_metadata('top_level.txt'):
                if (modname not in sys.modules or modname in nsp
                    or modname in _namespace_packages
                ):
                    continue
    
                fn = getattr(sys.modules[modname], '__file__', None)
                if fn and (normalize_path(fn).startswith(loc) or fn.startswith(loc)):
                    continue
                issue_warning(
                    "Module %s was already imported from %s, but %s is being added"
                    " to sys.path" % (modname, fn, self.location),
                )
    
        def has_version(self):
            try:
                self.version
            except ValueError:
                issue_warning("Unbuilt egg for "+repr(self))
                return False
            return True
    
        def clone(self,**kw):
            """Copy this distribution, substituting in any changed keyword args"""
            for attr in (
                'project_name', 'version', 'py_version', 'platform', 'location',
                'precedence'
            ):
                kw.setdefault(attr, getattr(self,attr,None))
            kw.setdefault('metadata', self._provider)
            return self.__class__(**kw)
    
    
    
    
        #@property
        def extras(self):
            return [dep for dep in self._dep_map if dep]
        extras = property(extras)
    
    
    def issue_warning(*args,**kw):
        level = 1
        g = globals()
        try:
            # find the first stack frame that is *not* code in
            # the pkg_resources module, to use for the warning
            while sys._getframe(level).f_globals is g:
                level += 1
        except ValueError:
            pass
        from warnings import warn
        warn(stacklevel = level+1, *args, **kw)
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    def parse_requirements(strs):
        """Yield ``Requirement`` objects for each specification in `strs`
    
        `strs` must be an instance of ``basestring``, or a (possibly-nested)
        iterable thereof.
        """
        # create a steppable iterator, so we can handle \-continuations
        lines = iter(yield_lines(strs))
    
        def scan_list(ITEM,TERMINATOR,line,p,groups,item_name):
    
            items = []
    
            while not TERMINATOR(line,p):
                if CONTINUE(line,p):
                    try:
                        line = lines.next(); p = 0
                    except StopIteration:
                        raise ValueError(
                            "\\ must not appear on the last nonblank line"
                        )
    
                match = ITEM(line,p)
                if not match:
                    raise ValueError("Expected "+item_name+" in",line,"at",line[p:])
    
                items.append(match.group(*groups))
                p = match.end()
    
                match = COMMA(line,p)
                if match:
                    p = match.end() # skip the comma
                elif not TERMINATOR(line,p):
                    raise ValueError(
                        "Expected ',' or end-of-list in",line,"at",line[p:]
                    )
    
            match = TERMINATOR(line,p)
            if match: p = match.end()   # skip the terminator, if any
            return line, p, items
    
        for line in lines:
            match = DISTRO(line)
            if not match:
                raise ValueError("Missing distribution spec", line)
            project_name = match.group(1)
            p = match.end()
            extras = []
    
            match = OBRACKET(line,p)
            if match:
                p = match.end()
                line, p, extras = scan_list(
                    DISTRO, CBRACKET, line, p, (1,), "'extra' name"
                )
    
            line, p, specs = scan_list(VERSION,LINE_END,line,p,(1,2),"version spec")
            specs = [(op,safe_version(val)) for op,val in specs]
            yield Requirement(project_name, specs, extras)
    
    
    def _sort_dists(dists):
        tmp = [(dist.hashcmp,dist) for dist in dists]
        tmp.sort()
        dists[::-1] = [d for hc,d in tmp]
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    
    class Requirement:
        def __init__(self, project_name, specs, extras):
            """DO NOT CALL THIS UNDOCUMENTED METHOD; use Requirement.parse()!"""
            self.unsafe_name, project_name = project_name, safe_name(project_name)
            self.project_name, self.key = project_name, project_name.lower()
            index = [(parse_version(v),state_machine[op],op,v) for op,v in specs]
            index.sort()
            self.specs = [(op,ver) for parsed,trans,op,ver in index]
            self.index, self.extras = index, tuple(map(safe_extra,extras))
            self.hashCmp = (
                self.key, tuple([(op,parsed) for parsed,trans,op,ver in index]),
                frozenset(self.extras)
            )
            self.__hash = hash(self.hashCmp)
    
        def __str__(self):
            specs = ','.join([''.join(s) for s in self.specs])
            extras = ','.join(self.extras)
            if extras: extras = '[%s]' % extras
            return '%s%s%s' % (self.project_name, extras, specs)
    
        def __eq__(self,other):
            return isinstance(other,Requirement) and self.hashCmp==other.hashCmp
    
        def __contains__(self,item):
            if isinstance(item,Distribution):
                if item.key != self.key: return False
                if self.index: item = item.parsed_version  # only get if we need it
            elif isinstance(item,basestring):
                item = parse_version(item)
            last = None
            for parsed,trans,op,ver in self.index:
                action = trans[cmp(item,parsed)]
                if action=='F':     return False
                elif action=='T':   return True
                elif action=='+':   last = True
                elif action=='-' or last is None:   last = False
            if last is None: last = True    # no rules encountered
            return last
    
    
        def __hash__(self):
            return self.__hash
    
        def __repr__(self): return "Requirement.parse(%r)" % str(self)
    
        #@staticmethod
        def parse(s):
            reqs = list(parse_requirements(s))
            if reqs:
                if len(reqs)==1:
                    return reqs[0]
                raise ValueError("Expected only one requirement", s)
            raise ValueError("No requirements found", s)
    
        parse = staticmethod(parse)
    
    state_machine = {
        #       =><
        '<' :  '--T',
        '<=':  'T-T',
        '>' :  'F+F',
        '>=':  'T+F',
        '==':  'T..',
        '!=':  'F++',
    }
    
    
    def _get_mro(cls):
        """Get an mro for a type or classic class"""
        if not isinstance(cls,type):
            class cls(cls,object): pass
            return cls.__mro__[1:]
        return cls.__mro__
    
    def _find_adapter(registry, ob):
        """Return an adapter factory for `ob` from `registry`"""
        for t in _get_mro(getattr(ob, '__class__', type(ob))):
            if t in registry:
                return registry[t]
    
    
    def ensure_directory(path):
        """Ensure that the parent directory of `path` exists"""
        dirname = os.path.dirname(path)
        if not os.path.isdir(dirname):
            os.makedirs(dirname)
    
    def split_sections(s):
        """Split a string or iterable thereof into (section,content) pairs
    
        Each ``section`` is a stripped version of the section header ("[section]")
        and each ``content`` is a list of stripped lines excluding blank lines and
        comment-only lines.  If there are any such lines before the first section
        header, they're returned in a first ``section`` of ``None``.
        """
        section = None
        content = []
        for line in yield_lines(s):
            if line.startswith("["):
                if line.endswith("]"):
                    if section or content:
                        yield section, content
                    section = line[1:-1].strip()
                    content = []
                else:
                    raise ValueError("Invalid section heading", line)
            else:
                content.append(line)
    
        # wrap up last segment
        yield section, content
    
    def _mkstemp(*args,**kw):
        from tempfile import mkstemp
        old_open = os.open
        try:
            os.open = os_open   # temporarily bypass sandboxing
            return mkstemp(*args,**kw)
        finally:
            os.open = old_open  # and then put it back
    
    
    # Set up global resource manager (deliberately not state-saved)
    _manager = ResourceManager()
    def _initialize(g):
        for name in dir(_manager):
            if not name.startswith('_'):
                g[name] = getattr(_manager, name)
    _initialize(globals())
    
    # Prepare the master working set and make the ``require()`` API available
    _declare_state('object', working_set = WorkingSet())
    try:
        # Does the main program list any requirements?
        from __main__ import __requires__
    except ImportError:
        pass # No: just use the default working set based on sys.path
    else:
        # Yes: ensure the requirements are met, by prefixing sys.path if necessary
        try:
            working_set.require(__requires__)
        except VersionConflict:     # try it without defaults already on sys.path
            working_set = WorkingSet([])    # by starting with an empty path
            for dist in working_set.resolve(
                parse_requirements(__requires__), Environment()
            ):
                working_set.add(dist)
            for entry in sys.path:  # add any missing entries from sys.path
                if entry not in working_set.entries:
                    working_set.add_entry(entry)
            sys.path[:] = working_set.entries   # then copy back to sys.path
    
    require = working_set.require
    iter_entry_points = working_set.iter_entry_points
    add_activation_listener = working_set.subscribe
    run_script = working_set.run_script
    run_main = run_script   # backward compatibility
    # Activate all distributions already on sys.path, and ensure that
    # all distributions added to the working set in the future (e.g. by
    # calling ``require()``) will get activated as well.
    add_activation_listener(lambda dist: dist.activate())
    working_set.entries=[]; map(working_set.add_entry,sys.path) # match order