295 lines
9.4 KiB
Python
295 lines
9.4 KiB
Python
"""Abstract base classes related to import."""
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from . import _bootstrap
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from . import machinery
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try:
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import _frozen_importlib
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except ModuleNotFoundError as exc:
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if exc.name != '_frozen_importlib':
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raise
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_frozen_importlib = None
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import abc
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def _register(abstract_cls, *classes):
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for cls in classes:
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abstract_cls.register(cls)
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if _frozen_importlib is not None:
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frozen_cls = getattr(_frozen_importlib, cls.__name__)
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abstract_cls.register(frozen_cls)
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class Finder(metaclass=abc.ABCMeta):
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"""Legacy abstract base class for import finders.
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It may be subclassed for compatibility with legacy third party
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reimplementations of the import system. Otherwise, finder
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implementations should derive from the more specific MetaPathFinder
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or PathEntryFinder ABCs.
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"""
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@abc.abstractmethod
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def find_module(self, fullname, path=None):
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"""An abstract method that should find a module.
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The fullname is a str and the optional path is a str or None.
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Returns a Loader object or None.
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"""
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class MetaPathFinder(Finder):
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"""Abstract base class for import finders on sys.meta_path."""
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@abc.abstractmethod
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def find_module(self, fullname, path):
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"""Abstract method which, when implemented, should find a module.
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The fullname is a str and the path is a list of strings or None.
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Returns a Loader object or None.
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"""
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def invalidate_caches(self):
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"""An optional method for clearing the finder's cache, if any.
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This method is used by importlib.invalidate_caches().
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"""
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_register(MetaPathFinder, machinery.BuiltinImporter, machinery.FrozenImporter,
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machinery.PathFinder, machinery.WindowsRegistryFinder)
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class PathEntryFinder(Finder):
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"""Abstract base class for path entry finders used by PathFinder."""
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@abc.abstractmethod
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def find_loader(self, fullname):
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"""Abstract method which, when implemented, returns a module loader or
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a possible part of a namespace.
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The fullname is a str. Returns a 2-tuple of (Loader, portion) where
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portion is a sequence of file system locations contributing to part of
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a namespace package. The sequence may be empty and the loader may be
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None.
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"""
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return None, []
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find_module = _bootstrap._find_module_shim
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def invalidate_caches(self):
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"""An optional method for clearing the finder's cache, if any.
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This method is used by PathFinder.invalidate_caches().
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"""
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_register(PathEntryFinder, machinery.FileFinder)
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class Loader(metaclass=abc.ABCMeta):
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"""Abstract base class for import loaders.
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The optional method module_repr(module) may be defined to provide a
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repr for a module when appropriate (see PEP 420). The __repr__() method on
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the module type will use the method as appropriate.
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"""
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@abc.abstractmethod
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def load_module(self, fullname):
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"""Abstract method which when implemented should load a module.
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The fullname is a str.
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ImportError is raised on failure.
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"""
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raise ImportError
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def module_repr(self, module):
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"""Return a module's repr.
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Used by the module type when the method does not raise
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NotImplementedError.
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"""
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raise NotImplementedError
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def init_module_attrs(self, module):
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"""Set the module's __loader__ attribute."""
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module.__loader__ = self
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class ResourceLoader(Loader):
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"""Abstract base class for loaders which can return data from their
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back-end storage.
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This ABC represents one of the optional protocols specified by PEP 302.
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"""
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@abc.abstractmethod
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def get_data(self, path):
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"""Abstract method which when implemented should return the bytes for
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the specified path. The path must be a str."""
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raise IOError
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class InspectLoader(Loader):
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"""Abstract base class for loaders which support inspection about the
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modules they can load.
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This ABC represents one of the optional protocols specified by PEP 302.
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"""
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@abc.abstractmethod
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def is_package(self, fullname):
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"""Abstract method which when implemented should return whether the
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module is a package. The fullname is a str. Returns a bool.
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Raises ImportError is the module cannot be found.
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"""
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raise ImportError
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def get_code(self, fullname):
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"""Method which returns the code object for the module.
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The fullname is a str. Returns a types.CodeType if possible, else
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returns None if a code object does not make sense
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(e.g. built-in module). Raises ImportError if the module cannot be
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found.
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"""
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source = self.get_source(fullname)
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if source is None:
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return None
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return self.source_to_code(source)
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@abc.abstractmethod
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def get_source(self, fullname):
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"""Abstract method which should return the source code for the
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module. The fullname is a str. Returns a str.
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Raises ImportError if the module cannot be found.
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"""
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raise ImportError
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def source_to_code(self, data, path='<string>'):
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"""Compile 'data' into a code object.
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The 'data' argument can be anything that compile() can handle. The'path'
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argument should be where the data was retrieved (when applicable)."""
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return compile(data, path, 'exec', dont_inherit=True)
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def init_module_attrs(self, module):
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"""Initialize the __loader__ and __package__ attributes of the module.
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The name of the module is gleaned from module.__name__. The __package__
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attribute is set based on self.is_package().
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"""
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super().init_module_attrs(module)
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_bootstrap._init_package_attrs(self, module)
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load_module = _bootstrap._LoaderBasics.load_module
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_register(InspectLoader, machinery.BuiltinImporter, machinery.FrozenImporter,
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machinery.ExtensionFileLoader)
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class ExecutionLoader(InspectLoader):
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"""Abstract base class for loaders that wish to support the execution of
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modules as scripts.
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This ABC represents one of the optional protocols specified in PEP 302.
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"""
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@abc.abstractmethod
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def get_filename(self, fullname):
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"""Abstract method which should return the value that __file__ is to be
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set to.
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Raises ImportError if the module cannot be found.
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"""
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raise ImportError
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def get_code(self, fullname):
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"""Method to return the code object for fullname.
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Should return None if not applicable (e.g. built-in module).
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Raise ImportError if the module cannot be found.
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"""
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source = self.get_source(fullname)
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if source is None:
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return None
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try:
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path = self.get_filename(fullname)
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except ImportError:
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return self.source_to_code(source)
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else:
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return self.source_to_code(source, path)
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def init_module_attrs(self, module):
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"""Initialize the module's attributes.
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It is assumed that the module's name has been set on module.__name__.
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It is also assumed that any path returned by self.get_filename() uses
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(one of) the operating system's path separator(s) to separate filenames
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from directories in order to set __path__ intelligently.
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InspectLoader.init_module_attrs() sets __loader__ and __package__.
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"""
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super().init_module_attrs(module)
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_bootstrap._init_file_attrs(self, module)
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class FileLoader(_bootstrap.FileLoader, ResourceLoader, ExecutionLoader):
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"""Abstract base class partially implementing the ResourceLoader and
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ExecutionLoader ABCs."""
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_register(FileLoader, machinery.SourceFileLoader,
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machinery.SourcelessFileLoader)
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class SourceLoader(_bootstrap.SourceLoader, ResourceLoader, ExecutionLoader):
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"""Abstract base class for loading source code (and optionally any
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corresponding bytecode).
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To support loading from source code, the abstractmethods inherited from
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ResourceLoader and ExecutionLoader need to be implemented. To also support
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loading from bytecode, the optional methods specified directly by this ABC
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is required.
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Inherited abstractmethods not implemented in this ABC:
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* ResourceLoader.get_data
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* ExecutionLoader.get_filename
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"""
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def path_mtime(self, path):
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"""Return the (int) modification time for the path (str)."""
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if self.path_stats.__func__ is SourceLoader.path_stats:
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raise IOError
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return int(self.path_stats(path)['mtime'])
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def path_stats(self, path):
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"""Return a metadata dict for the source pointed to by the path (str).
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Possible keys:
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- 'mtime' (mandatory) is the numeric timestamp of last source
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code modification;
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- 'size' (optional) is the size in bytes of the source code.
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"""
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if self.path_mtime.__func__ is SourceLoader.path_mtime:
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raise IOError
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return {'mtime': self.path_mtime(path)}
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def set_data(self, path, data):
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"""Write the bytes to the path (if possible).
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Accepts a str path and data as bytes.
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Any needed intermediary directories are to be created. If for some
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reason the file cannot be written because of permissions, fail
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silently.
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"""
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_register(SourceLoader, machinery.SourceFileLoader)
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