files.py 文件源码

def canonical_filename(filename):
    """Return a canonical file name for `filename`.

    An absolute path with no redundant components and normalized case.

    """
    if filename not in CANONICAL_FILENAME_CACHE:
        if not os.path.isabs(filename):
            for path in [os.curdir] + sys.path:
                if path is None:
                    continue
                f = os.path.join(path, filename)
                if os.path.exists(f):
                    filename = f
                    break
        cf = abs_file(filename)
        CANONICAL_FILENAME_CACHE[filename] = cf
    return CANONICAL_FILENAME_CACHE[filename]