def realpath(*args):
if None in args:<EOL><INDENT>return None<EOL><DEDENT>return os.path.realpath(<EOL>os.path.expandvars(os.path.expanduser(os.path.join(*args))))<EOL>
Join all args and return the real path, rooted at /.

    Expands ``~`` and environment variables such as :envvar:`$HOME`.

    Returns ``None`` if any of the args is none.