The road of python self-study (6) regular

Regular

use:

import re
re.match(pattern,string,flags = 0)
pa = re.match('love','i love you')  //从头开始匹配
pa.group()  //匹配对象
pa.span() //匹配位置元组
功能:从第一个字符开始匹配 不符合返回None

re.search(pattern,string,flags = 0)
pa =re.search('love','i love you')
功能:扫描整个字符串  返回值是第一个出现的

findall(pattern,string,flags = 0)
功能:查找整个字符串 结果返回列表

compile 
功能:正则表达式是否正确

single character

==.== matches any character except a newline

==[]== The matching set is any character in []

==az== matches characters other than az

==^== Boundary starts with ..

==$== delimiter ends with ..

==[a-zA-Z0-9]== matches alphanumeric characters

==\d== matches numbers

==\D== matches non-digits

==\w== matches alphanumeric underscore

==\W== matches non-alphanumeric underscores

==\s== matches the null character

==\S== any character except whitespace

=={n}== Modifies the single character before the metacharacter n times

=={n,}== The single character preceding the modifier metacharacter appears at least n times

=={n,m}== The single character before the modifier metacharacter appears >=n <=m times

=={,n}== modifier metacharacter occurrences are 0-n

==+== At least 1 occurrence of a single character before the modifier metacharacter

==*== can match 0 times or any number of times

==? == matches once or 0 times

==\b== Word boundaries\W are separated by word boundaries

==\B== non-word boundary

r'\w' 修饰正则表达式时意义和修饰字符串时意义不同 
修饰字符串的时候是失去转义字符的意义
在正则里 是不进行转义

Grouping and Subpatterns

==()== subpattern

==\num== Use the value matched in num times () as the matching character

\w \S can match Chinese

Understand: (?P) (?P=name)

greedy mode

regex default greedy mode

Commonly used non-greedy patterns

==+?==

==*?==

expression modifier

re.I ignore character size

re.M as multiple lines

re.S is treated as a single line

Regular function

sub replace

sub(字符串,源字符串)
reg = re.compile(r'\d'')
res = reg.sub('aa','woyi12')
print(res)   //woyaa

Note:

1. When using findall to match, () in the regular expression is the capture type to get the content of the parentheses in the matched result
2. (?:) non-capturing parentheses match pattern but do not capture

Regular iterator

res = re.finditer('\d','12345')
print(next(res).group())  //1
print(next(res).group())  //2
print(next(res).group())  //3