Modules commonly used in the python and regular expressions re module

First, the regular expression:

Regular expressions not used in python, but is available in all languages. Just call the method varies.

#在python中纯代码校验手机号码：
while True:
    phone_number = input('please input your phone number ：')
    if len(phone_number) == 11 \
            and phone_number.isdigit()\
            and (phone_number.startswith('13') \
            or phone_number.startswith('14') \
            or phone_number.startswith('15') \
            or phone_number.startswith('16')\
            or phone_number.startswith ( ' 17 ' ) \
             or phone_number.startswith ( ' 18 ' )):
         Print ( ' legitimate phone number ' )
     the else :
         Print ( ' is not a valid phone number ' )

# Re calls in python modules use regular expressions to check the phone number:

Import Re 
PHONE_NUMBER = INPUT ( ' Please INPUT your Phone Number: ' )
 IF re.match ( ' ^ (13 is | 14 | 15 | 16 |. 17 | 18 is) [0-9]. 9} {$ ' , PHONE_NUMBER):
         Print ( ' a legitimate phone number ' )
 the else :
         Print ( ' is not a valid phone number ' )

Conclusion: The call re module in python using regular expressions will be simple lot.

Regular expression syntax is as follows:

Which quantifier '*', '+', '? 'Are greedy matching is to match the character more times, if a quantifier behind the increase'? 'This symbol, it means an inert match, in other words to try to match less.

Embodied in matching real column as follows:

1. '.', '^', '$' Three specific performance

2.'? ',' + ',' * ',' {} 'Embodied

When coupled with the quantifier '? 'Changed.

3 '[^] *' usage:

Second, the combination of several conventional greedy summary matches

Third, greedy matching and non-matching greedy

1.<.*>:先拿着里面的.*去匹配所有的内容，然后再根据>找到最后一个>为止。

2.<.*?>:先拿着?后面的>，在字符中碰到第一个>就停止。

re模块的使用：

三个必须掌握的方法有如下

1.findall

import re

res = re.findall('c','andy cody jcason') #查找字符串中所有‘c’字符

print(res)#返回所有的满足匹配条件的放在列表里, ['c','c']

　findall 查找所有字符，只要是能匹配到的字符，全部放在一个列表里，不需要调用group方法。　

2.search

import re
res = re.search('c','ancdy cody jcason')
print(res.group()) #用group方法

search 查找所有字符，只要找到第一个匹配到的字符后会停止查找，并返回匹配的字符。

全部字符中如果没有要找的字符，就会返回None，如果用group方法调用就会报错。

3.match

import re

res = re.match('c','cncdy cody jcason')

print(res.group()) #‘c’

match 只会找字符中的开头字符是否含有所匹配的字符，有就会返回匹配的字符

如果字符开头不是要找的字符，就会返回None, 如果用group方法调用就会报错

其他涉及到的使用方法：

1.split

ret = re.split('[ab]', 'abcd')  # 先按'a'分割得到''和'bcd',再对''和'bcd'分别按'b'分割
print(ret)  # ['', '', 'cd']

2.sub

ret = re.sub('\d', 'W', '3andy4cody4', 1)   # 将数字替换成'W'，参数1表示只替换1个
print(ret)  # Wandy4cody4

3.subn

ret = re.subn('\d', 'W', '3andy4cody4', 1)   # 将数字替换成'W'
print(ret)  # WandyWcodyW  返回元组(替换的结果,替换了多少次)

4.compile

obj = re.compile('\d{3}')  #将正则表达式编译成为一个 正则表达式对象，规则要匹配的是3个数字
ret = obj.search('abc123eeee') #正则表达式对象调用search，参数为待匹配的字符串
print(ret.group())  #结果 ： 123

Modules commonly used in the python and regular expressions re module

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