Python sys.meta_path() Examples

def find_loader(name, path=None):
    """Find the loader for the specified module.

    First, sys.modules is checked to see if the module was already imported. If
    so, then sys.modules[name].__loader__ is returned. If that happens to be
    set to None, then ValueError is raised. If the module is not in
    sys.modules, then sys.meta_path is searched for a suitable loader with the
    value of 'path' given to the finders. None is returned if no loader could
    be found.

    Dotted names do not have their parent packages implicitly imported. You will
    most likely need to explicitly import all parent packages in the proper
    order for a submodule to get the correct loader.

    """
    try:
        loader = sys.modules[name].__loader__
        if loader is None:
            raise ValueError('{}.__loader__ is None'.format(name))
        else:
            return loader
    except KeyError:
        pass
    return _bootstrap._find_module(name, path) 

def remove_hooks(scrub_sys_modules=False):
    """
    This function removes the import hook from sys.meta_path.
    """
    if PY3:
        return
    flog.debug('Uninstalling hooks ...')
    # Loop backwards, so deleting items keeps the ordering:
    for i, hook in list(enumerate(sys.meta_path))[::-1]:
        if hasattr(hook, 'RENAMER'):
            del sys.meta_path[i]

    # Explicit is better than implicit. In the future the interface should
    # probably change so that scrubbing the import hooks requires a separate
    # function call. Left as is for now for backward compatibility with
    # v0.11.x.
    if scrub_sys_modules:
        scrub_future_sys_modules() 

def install_hooks():
    """
    This function installs the future.standard_library import hook into
    sys.meta_path.
    """
    if PY3:
        return

    install_aliases()

    flog.debug('sys.meta_path was: {0}'.format(sys.meta_path))
    flog.debug('Installing hooks ...')

    # Add it unless it's there already
    newhook = RenameImport(RENAMES)
    if not detect_hooks():
        sys.meta_path.append(newhook)
    flog.debug('sys.meta_path is now: {0}'.format(sys.meta_path)) 

def remove_hooks(scrub_sys_modules=False):
    """
    This function removes the import hook from sys.meta_path.
    """
    if PY3:
        return
    flog.debug('Uninstalling hooks ...')
    # Loop backwards, so deleting items keeps the ordering:
    for i, hook in list(enumerate(sys.meta_path))[::-1]:
        if hasattr(hook, 'RENAMER'):
            del sys.meta_path[i]

    # Explicit is better than implicit. In the future the interface should
    # probably change so that scrubbing the import hooks requires a separate
    # function call. Left as is for now for backward compatibility with
    # v0.11.x.
    if scrub_sys_modules:
        scrub_future_sys_modules() 

def detect_hooks():
    """
    Returns True if the import hooks are installed, False if not.
    """
    flog.debug('Detecting hooks ...')
    present = any([hasattr(hook, 'RENAMER') for hook in sys.meta_path])
    if present:
        flog.debug('Detected.')
    else:
        flog.debug('Not detected.')
    return present


# As of v0.12, this no longer happens implicitly:
# if not PY3:
#     install_hooks() 

def install_hooks():
    """
    This function installs the future.standard_library import hook into
    sys.meta_path.
    """
    if PY3:
        return

    install_aliases()

    flog.debug('sys.meta_path was: {0}'.format(sys.meta_path))
    flog.debug('Installing hooks ...')

    # Add it unless it's there already
    newhook = RenameImport(RENAMES)
    if not detect_hooks():
        sys.meta_path.append(newhook)
    flog.debug('sys.meta_path is now: {0}'.format(sys.meta_path)) 

def install_hooks():
    """
    This function installs the future.standard_library import hook into
    sys.meta_path.
    """
    if PY3:
        return

    install_aliases()

    flog.debug('sys.meta_path was: {0}'.format(sys.meta_path))
    flog.debug('Installing hooks ...')

    # Add it unless it's there already
    newhook = RenameImport(RENAMES)
    if not detect_hooks():
        sys.meta_path.append(newhook)
    flog.debug('sys.meta_path is now: {0}'.format(sys.meta_path)) 

def remove_hooks(scrub_sys_modules=False):
    """
    This function removes the import hook from sys.meta_path.
    """
    if PY3:
        return
    flog.debug('Uninstalling hooks ...')
    # Loop backwards, so deleting items keeps the ordering:
    for i, hook in list(enumerate(sys.meta_path))[::-1]:
        if hasattr(hook, 'RENAMER'):
            del sys.meta_path[i]

    # Explicit is better than implicit. In the future the interface should
    # probably change so that scrubbing the import hooks requires a separate
    # function call. Left as is for now for backward compatibility with
    # v0.11.x.
    if scrub_sys_modules:
        scrub_future_sys_modules() 

def mount(self, append=False):
        pathname = os.path.abspath(os.path.join(self.dirname, self.filename))
        if not self.is_compatible():
            msg = 'Wheel %s not compatible with this Python.' % pathname
            raise DistlibException(msg)
        if not self.is_mountable():
            msg = 'Wheel %s is marked as not mountable.' % pathname
            raise DistlibException(msg)
        if pathname in sys.path:
            logger.debug('%s already in path', pathname)
        else:
            if append:
                sys.path.append(pathname)
            else:
                sys.path.insert(0, pathname)
            extensions = self._get_extensions()
            if extensions:
                if _hook not in sys.meta_path:
                    sys.meta_path.append(_hook)
                _hook.add(pathname, extensions) 

def _FakeProxyBypassHelper(fn,
                             original_module_dict=sys.modules.copy(),
                             original_uname=os.uname):
    """Setups and restores the state for the Mac OS X urllib fakes."""
    def Inner(*args, **kwargs):
      current_uname = os.uname
      current_meta_path = sys.meta_path[:]
      current_modules = sys.modules.copy()

      try:
        sys.modules.clear()
        sys.modules.update(original_module_dict)
        sys.meta_path[:] = []
        os.uname = original_uname

        return fn(*args, **kwargs)
      finally:
        sys.modules.clear()
        sys.modules.update(current_modules)
        os.uname = current_uname
        sys.meta_path[:] = current_meta_path
    return Inner 

def ResetModules(self):
    """Clear modules so that when request is run they are reloaded."""
    lib_config._default_registry.reset()
    self._modules.clear()
    self._modules.update(self._default_modules)


    sys.path_hooks[:] = self._save_path_hooks


    sys.meta_path = []





    apiproxy_stub_map.apiproxy.GetPreCallHooks().Clear()
    apiproxy_stub_map.apiproxy.GetPostCallHooks().Clear() 

def mount(self, append=False):
        pathname = os.path.abspath(os.path.join(self.dirname, self.filename))
        if not self.is_compatible():
            msg = 'Wheel %s not compatible with this Python.' % pathname
            raise DistlibException(msg)
        if not self.is_mountable():
            msg = 'Wheel %s is marked as not mountable.' % pathname
            raise DistlibException(msg)
        if pathname in sys.path:
            logger.debug('%s already in path', pathname)
        else:
            if append:
                sys.path.append(pathname)
            else:
                sys.path.insert(0, pathname)
            extensions = self._get_extensions()
            if extensions:
                if _hook not in sys.meta_path:
                    sys.meta_path.append(_hook)
                _hook.add(pathname, extensions) 

def register_assert_rewrite(*names):
    """Register one or more module names to be rewritten on import.

    This function will make sure that this module or all modules inside
    the package will get their assert statements rewritten.
    Thus you should make sure to call this before the module is
    actually imported, usually in your __init__.py if you are a plugin
    using a package.

    :raise TypeError: if the given module names are not strings.
    """
    for name in names:
        if not isinstance(name, str):
            msg = "expected module names as *args, got {0} instead"
            raise TypeError(msg.format(repr(names)))
    for hook in sys.meta_path:
        if isinstance(hook, rewrite.AssertionRewritingHook):
            importhook = hook
            break
    else:
        importhook = DummyRewriteHook()
    importhook.mark_rewrite(*names) 

def _add_git_repo(url_builder, username=None, repo=None, module=None, branch=None, commit=None, **kw):
    '''
Function that creates and adds to the 'sys.meta_path' an HttpImporter object equipped with a URL of a Online Git server.
The 'url_builder' parameter is a function that accepts the username, repo and branch/commit, and creates a HTTP/S URL of a Git server. Compatible functions are '__create_github_url', '__create_bitbucket_url'.
The 'username' parameter defines the Github username which is the repository's owner.
The 'repo' parameter defines the name of the repo that contains the modules/packages to be imported.
The 'module' parameter is optional and is a list containing the modules/packages that are available in the chosen Github repository.
If it is not provided, it defaults to the repositories name, as it is common that the a Python repository at "github.com/someuser/somereponame" contains a module/package of "somereponame".
The 'branch' and 'commit' parameters cannot be both populated at the same call. They specify the branch (last commit) or specific commit, that should be served.
    '''
    if username == None or repo == None:
        raise Error("'username' and 'repo' parameters cannot be None")
    if commit and branch:
        raise Error("'branch' and 'commit' parameters cannot be both set!")

    if commit:
        branch = commit
    if not branch:
        branch = 'master'
    if not module:
        module = repo
    if type(module) == str:
        module = [module]
    url = url_builder(username, repo, branch, **kw)
    return add_remote_repo(module, url) 

def mount(self, append=False):
        pathname = os.path.abspath(os.path.join(self.dirname, self.filename))
        if not self.is_compatible():
            msg = 'Wheel %s not compatible with this Python.' % pathname
            raise DistlibException(msg)
        if not self.is_mountable():
            msg = 'Wheel %s is marked as not mountable.' % pathname
            raise DistlibException(msg)
        if pathname in sys.path:
            logger.debug('%s already in path', pathname)
        else:
            if append:
                sys.path.append(pathname)
            else:
                sys.path.insert(0, pathname)
            extensions = self._get_extensions()
            if extensions:
                if _hook not in sys.meta_path:
                    sys.meta_path.append(_hook)
                _hook.add(pathname, extensions) 

def mount(self, append=False):
        pathname = os.path.abspath(os.path.join(self.dirname, self.filename))
        if not self.is_compatible():
            msg = 'Wheel %s not compatible with this Python.' % pathname
            raise DistlibException(msg)
        if not self.is_mountable():
            msg = 'Wheel %s is marked as not mountable.' % pathname
            raise DistlibException(msg)
        if pathname in sys.path:
            logger.debug('%s already in path', pathname)
        else:
            if append:
                sys.path.append(pathname)
            else:
                sys.path.insert(0, pathname)
            extensions = self._get_extensions()
            if extensions:
                if _hook not in sys.meta_path:
                    sys.meta_path.append(_hook)
                _hook.add(pathname, extensions) 

def load_module(self, fullname):
        print('load_module {}'.format(fullname))
        if fullname in sys.modules:
            return sys.modules[fullname]

        # 先从 sys.meta_path 中删除自定义的 finder
        # 防止下面执行 import_module 的时候再次触发此 finder
        # 从而出现递归调用的问题
        finder = sys.meta_path.pop(0)
        # 导入 module
        module = importlib.import_module(fullname)

        module_hook(fullname, module)

        sys.meta_path.insert(0, finder)
        return module 

def load_module(self, fullname):
        print('load_module {}'.format(fullname))
        if fullname in sys.modules:
            return sys.modules[fullname]

        # 先从 sys.meta_path 中删除自定义的 finder
        # 防止下面执行 import_module 的时候再次触发此 finder
        # 从而出现递归调用的问题
        finder = sys.meta_path.pop(0)
        # 导入 module
        module = importlib.import_module(fullname)

        module_hook(fullname, module)

        sys.meta_path.insert(0, finder)
        return module 

def load_module(self, fullname):
        print('load_module {}'.format(fullname))
        if fullname in sys.modules:
            return sys.modules[fullname]

        # 先从 sys.meta_path 中删除自定义的 finder
        # 防止下面执行 import_module 的时候再次触发此 finder
        # 从而出现递归调用的问题
        finder = sys.meta_path.pop(0)
        # 导入 module
        module = importlib.import_module(fullname)

        module_hook(fullname, module)

        sys.meta_path.insert(0, finder)
        return module 

def invalidate_caches():
    """Call the invalidate_caches() method on all meta path finders stored in
    sys.meta_path (where implemented)."""
    for finder in sys.meta_path:
        if hasattr(finder, 'invalidate_caches'):
            finder.invalidate_caches() 

def _unload_pkg_resources():
    sys.meta_path = [
        importer
        for importer in sys.meta_path
        if importer.__class__.__module__ != 'pkg_resources.extern'
    ]
    del_modules = [
        name for name in sys.modules
        if name.startswith('pkg_resources')
    ]
    for mod_name in del_modules:
        del sys.modules[mod_name] 

def install_hooks(include_paths=(), exclude_paths=()):
    if isinstance(include_paths, str):
        include_paths = (include_paths,)
    if isinstance(exclude_paths, str):
        exclude_paths = (exclude_paths,)
    assert len(include_paths) + len(exclude_paths) > 0, 'Pass at least one argument'
    _hook.include(include_paths)
    _hook.exclude(exclude_paths)
    # _hook.debug = debug
    enable = sys.version_info[0] >= 3   # enabled for all 3.x
    if enable and _hook not in sys.meta_path:
        sys.meta_path.insert(0, _hook)  # insert at beginning. This could be made a parameter

    # We could return the hook when there are ways of configuring it
    #return _hook 

def remove_hooks():
    if _hook in sys.meta_path:
        sys.meta_path.remove(_hook) 

def detect_hooks():
    """
    Returns True if the import hooks are installed, False if not.
    """
    return _hook in sys.meta_path
    # present = any([hasattr(hook, 'PY2FIXER') for hook in sys.meta_path])
    # return present 

def install_hooks(include_paths=(), exclude_paths=()):
    if isinstance(include_paths, str):
        include_paths = (include_paths,)
    if isinstance(exclude_paths, str):
        exclude_paths = (exclude_paths,)
    assert len(include_paths) + len(exclude_paths) > 0, 'Pass at least one argument'
    _hook.include(include_paths)
    _hook.exclude(exclude_paths)
    # _hook.debug = debug
    enable = sys.version_info[0] >= 3   # enabled for all 3.x
    if enable and _hook not in sys.meta_path:
        sys.meta_path.insert(0, _hook)  # insert at beginning. This could be made a parameter

    # We could return the hook when there are ways of configuring it
    #return _hook 

def remove_hooks():
    if _hook in sys.meta_path:
        sys.meta_path.remove(_hook) 

def detect_hooks():
    """
    Returns True if the import hooks are installed, False if not.
    """
    return _hook in sys.meta_path
    # present = any([hasattr(hook, 'PY2FIXER') for hook in sys.meta_path])
    # return present 

def _common_post_process(args):
  # TODO(iannucci): We should always do logging.basicConfig() (probably with
  # logging.WARNING), even if no verbose is passed. However we need to be
  # careful as this could cause issues with spurious/unexpected output.
  # Once the recipe engine is on native build.proto, this should be safe to
  # do.
  if args.verbose > 0:
    logging.basicConfig()
    logging.getLogger().setLevel(logging.INFO)
    if args.verbose > 1:
      logging.getLogger().setLevel(logging.DEBUG)
  else:
    # Prevent spurious "No handlers could be found for ..." stderr messages.
    # Once we always set a basicConfig (per TODO above), this can go away as
    # well.
    logging.root.manager.emittedNoHandlerWarning = True

  args.recipe_deps = RecipeDeps.create(
      args.main_repo_path,
      args.repo_override,
      args.proto_override,
  )

  _check_recipes_cfg_consistency(args.recipe_deps)

  # Allows:
  #   import RECIPE_MODULES.repo_name.module_name.submodule
  sys.meta_path = [RecipeModuleImporter(args.recipe_deps)] + sys.meta_path

  _cleanup_pyc(args.recipe_deps)

  # Remove flags that subcommands shouldn't use; everything from this point on
  # should ONLY use args.recipe_deps.
  del args.main_repo_path
  del args.verbose
  del args.repo_override 

def unmount(self):
        pathname = os.path.abspath(os.path.join(self.dirname, self.filename))
        if pathname not in sys.path:
            logger.debug('%s not in path', pathname)
        else:
            sys.path.remove(pathname)
            if pathname in _hook.impure_wheels:
                _hook.remove(pathname)
            if not _hook.impure_wheels:
                if _hook in sys.meta_path:
                    sys.meta_path.remove(_hook) 

def setUp(self):
    super(SandboxTest, self).setUp()
    self.mox = mox.Mox()
    self.old_path = sys.path
    self.old_meta_path = sys.meta_path
    self.old_library_format_string = sandbox._THIRD_PARTY_LIBRARY_FORMAT_STRING
    self.config = runtime_config_pb2.Config()
    self.app_root = 'test/app/root'
    self.config.application_root = self.app_root
    self.config.app_id = 'app'
    self.config.version_id = '1'
    self.builtins = __builtin__.__dict__.copy()
    self.modules = sys.modules.copy()