Module aws_lambda_powertools.shared.lazy_import

A LazyLoader class.

Classes

class LazyLoader (local_name, parent_module_globals, name)

Lazily import a module, mainly to avoid pulling in large dependencies.

contrib, and ffmpeg are examples of modules that are large and not always needed, and this allows them to only be loaded when they are used.

Note: Subclassing types.ModuleType allow us to correctly adhere with sys.modules, import system

Expand source code

class LazyLoader(types.ModuleType):
    """Lazily import a module, mainly to avoid pulling in large dependencies.

    `contrib`, and `ffmpeg` are examples of modules that are large and not always
    needed, and this allows them to only be loaded when they are used.

    Note: Subclassing types.ModuleType allow us to correctly adhere with sys.modules, import system
    """

    def __init__(self, local_name, parent_module_globals, name):  # pylint: disable=super-on-old-class
        self._local_name = local_name
        self._parent_module_globals = parent_module_globals

        super().__init__(name)

    def _load(self):
        # Import the target module and insert it into the parent's namespace
        module = importlib.import_module(self.__name__)
        self._parent_module_globals[self._local_name] = module

        # Update this object's dict so that if someone keeps a reference to the
        #   LazyLoader, lookups are efficient (__getattr__ is only called on lookups
        #   that fail).
        self.__dict__.update(module.__dict__)

        return module

    def __getattr__(self, item):
        module = self._load()
        return getattr(module, item)

    def __dir__(self):
        module = self._load()
        return dir(module)

Ancestors

• builtins.module