Converts a regex matching url to one that can be used with flask

def convert_regex_to_flask_path(url_path):
    """
    Converts a regex matching url to one that can be used with flask
    """
    for token in ["$"]:
        url_path = url_path.replace(token, "")

    def caller(reg):
        match_name, match_pattern = reg.groups()
        return '<regex("{0}"):{1}>'.format(match_pattern, match_name)

    url_path = re.sub("\(\?P<(.*?)>(.*?)\)", caller, url_path)

    if url_path.endswith("/?"):
        # Flask does own handling of trailing slashes
        url_path = url_path.rstrip("/?")
    return url_path