re例子，仅供参考

import re
匹配字符串
# pattern = re.compile(r'hello')
# match = pattern.search('ni hello cxy61!') #全字符匹配字符串 .search()
# search = pattern.match('ai hello') #只在开头匹配字符串  .match()
# if match:
#     print(match.group())
# else:
#     print('no match.')
#
# if search:
#     print(search.group())
# else:
#     print('no search')

替换
time = '2017-10-01'
pattern = re.compile(r'D')  #匹配非数字的字符
sub = pattern.sub('/',time) #替换非数字的字符
print(sub)
print(re.sub(r'D','/',time)) #也可以这样写，re.sub(表达式,替换字符,内容)
#D非数字的,'/'替换字符，time目标；把time里面非数字的都替换为/