将正则表达式中的捕获组转换为非捕获组

re_flatten.py

# borrow from bottle.py
def _re_flatten(p):
    ''' Turn all capturing groups in a regular expression pattern into
        non-capturing groups. '''
    if '(' not in p: return p
    return re.sub(r'(\\*)(\(\?P<[^>]+>|\((?!\?))',
        lambda m: m.group(0) if len(m.group(1)) % 2 else m.group(1) + '(?:', p)