python笔记54-re正则匹配替换字符串(sub和subn)

def sub(pattern, repl, string, count=0, flags=0):
    """Return the string obtained by replacing the leftmost
    non-overlapping occurrences of the pattern in string by the
    replacement repl.  repl can be either a string or a callable;
    if a string, backslash escapes in it are processed.  If it is
    a callable, it's passed the match object and must return
    a replacement string to be used."""
    return _compile(pattern, flags).sub(repl, string, count)

import re
'''
替换字符串中的数字为*号
'''
s = '作者-上海悠悠 QQ交流群:717225969 blog地址:https://www.cnblogs.com/yoyoketang/ 欢迎收藏'

new = re.sub("[0-9]", "*", s)
print(new)
# 作者-上海悠悠 QQ交流群:********* blog地址:https://www.cnblogs.com/yoyoketang/ 欢迎收藏

import re
'''
替换s中的空格为%20
'''
s = "We are happy."
print(re.sub(r' ', "%20", s))

# We%20are%20happy.

import re
'''
把字符串中的连续数字替换成hello
'''
s = "the number 200-40-3000"
print(re.sub(r'[\d]+', "hello", s))

# the number hello-hello-hello

import re
'''
替换时间格式 01/11/2021 替换成 2021/01/11
'''

s = "today is 01-11-2021."
day = re.sub(r'(\d{2})-(\d{2})-(\d{4})', r'\3-\2-\1', s)
print(day) # today is 2021-11-01.

# 也可以用g<3>-g<2>-g<1>
day2 = re.sub(r'(\d{2})-(\d{2})-(\d{4})', r'g<3>-g<2>-g<1>', s)
print(day) # today is 2021-11-01.

import re
'''
匹配字符串中的数字加2
'''

def addAge(match) ->str:
    '''返回匹配的值加2'''
    age = match.group()
    return str(int(age)+2)

s = 'my age is 20'
# repl 如果它是可调用的函数对象，则传递match对象，并且必须返回要使用的替换字符串
x = re.sub(r'[\d]+', addAge, s)
print(x)
# my age is 22

import re

'''
替换字符串中的空格为%20，只替换一次
'''
s = "We are happy."
print(re.sub(" ", "%20", s, count=1))

# We%20are happy.

import re

'''
替换字符串中的空格为%20，只替换一次
'''
s = "We are happy."
x, n = re.subn(" ", "%20", s, )
print("替换后：", x)
print("替换次数: ", n)