Function source_from_cache

Lib/importlib/_bootstrap_external.py:299–336

Given the path to a .pyc. file, return the path to its .py file. The .pyc file does not need to exist; this simply returns the path to the .py file calculated to correspond to the .pyc file. If path does not conform to PEP 3147/488 format, ValueError will be raised. If sys.implemen

(path)

def source_from_cache(path):
    """Given the path to a .pyc. file, return the path to its .py file.

    The .pyc file does not need to exist; this simply returns the path to
    the .py file calculated to correspond to the .pyc file.  If path does
    not conform to PEP 3147/488 format, ValueError will be raised. If
    sys.implementation.cache_tag is None then NotImplementedError is raised.

    """
    if sys.implementation.cache_tag is None:
        raise NotImplementedError('sys.implementation.cache_tag is None')
    path = _os.fspath(path)
    head, pycache_filename = _path_split(path)
    found_in_pycache_prefix = False
    if sys.pycache_prefix is not None:
        stripped_path = sys.pycache_prefix.rstrip(path_separators)
        if head.startswith(stripped_path + path_sep):
            head = head[len(stripped_path):]
            found_in_pycache_prefix = True
    if not found_in_pycache_prefix:
        head, pycache = _path_split(head)
        if pycache != _PYCACHE:
            raise ValueError(f'{_PYCACHE} not bottom-level directory in '
                             f'{path!r}')
    dot_count = pycache_filename.count('.')
    if dot_count not in {2, 3}:
        raise ValueError(f'expected only 2 or 3 dots in {pycache_filename!r}')
    elif dot_count == 3:
        optimization = pycache_filename.rsplit('.', 2)[-2]
        if not optimization.startswith(_OPT):
            raise ValueError("optimization portion of filename does not start "
                             f"with {_OPT!r}")
        opt_level = optimization[len(_OPT):]
        if not opt_level.isalnum():
            raise ValueError(f"optimization level {optimization!r} is not an "
                             "alphanumeric value")
    base_filename = pycache_filename.partition('.')[0]
    return _path_join(head, base_filename + SOURCE_SUFFIXES[0])


def _get_sourcefile(bytecode_path):