python 4-3如何调整字符串中文本的格式

读入一个日志文件，把里面的时间格式换成另外一种格式，用到了re模块正则表达式的分组

file = open("./catalina.2016-11-02.log").read()    
import re 
result = re.sub(r'(\d{2}), (\d{4}) (\d{2}):(\d{2}):(\d{2})', r'\2,\1,\5:\4:\3', file)
result = re.sub(r'(?P<day>\d{2}), (?P<year>\d{4}) (?P<hour>\d{2}):(?P<minute>\d{2}):(?P<second>\d{2})', r'\g<year>,\g<day>,\g<second>:\g<minute>:\g<hour>', file)
print(result)