re.sub参数之回调函数

from calendar import month_abbr
import re

def change_date(m):
    mon_name = month_abbr[int(m.group(1))]
    return '{} {} {}'.format(m.group(2), mon_name, m.group(3))

if __name__ == '__main__':
    text = 'Today is 11/27/2012. PyCon starts 3/13/2013.'
    datepat = re.compile(r'(\d+)/(\d+)/(\d+)')
    # 先会执行匹配，然后将匹配到的match对象传入到回调函数中
    print(datepat.sub(change_date, text))

def matchcase(word):
    def replace(m):
        text = m.group()
        if text.isupper():
            return word.upper()
        elif text.islower():
            return word.lower()
        elif text[0].isupper():
            return word.capitalize()
        else:
            return word
    return replace
if __name__ == '__main__':
  re.sub('python', matchcase('snake'), text, flags=re.IGNORECASE)