os.py 文件源码

def _fspath(path):
    """Return the path representation of a path-like object.

    If str or bytes is passed in, it is returned unchanged. Otherwise the
    os.PathLike interface is used to get the path representation. If the
    path representation is not str or bytes, TypeError is raised. If the
    provided path is not str, bytes, or os.PathLike, TypeError is raised.
    """
    if isinstance(path, (str, bytes)):
        return path

    # Work from the object's type to match method resolution of other magic
    # methods.
    path_type = type(path)
    try:
        path_repr = path_type.__fspath__(path)
    except AttributeError:
        if hasattr(path_type, '__fspath__'):
            raise
        else:
            raise TypeError("expected str, bytes or os.PathLike object, "
                            "not " + path_type.__name__)
    if isinstance(path_repr, (str, bytes)):
        return path_repr
    else:
        raise TypeError("expected {}.__fspath__() to return str or bytes, "
                        "not {}".format(path_type.__name__,
                                        type(path_repr).__name__))

# If there is no C implementation, make the pure Python version the
# implementation as transparently as possible.