_stdlib.py 文件源码

def expandvars(path):
    """
    Args:
        path (pathlike): A path to expand
    Returns:
        `fsnative`

    Like :func:`python:os.path.expandvars` but supports unicode under Windows
    + Python 2 and always returns a `fsnative`.
    """

    path = path2fsn(path)

    def repl_func(match):
        return environ.get(match.group(1), match.group(0))

    path = re.compile(r"\$(\w+)", flags=re.UNICODE).sub(repl_func, path)
    if os.name == "nt":
        path = re.sub(r"%([^%]+)%", repl_func, path)
    return re.sub(r"\$\{([^\}]+)\}", repl_func, path)