（学习）python非贪婪、多行匹配正则表达式例子

一些regular的tips：

1 非贪婪flag

>>> re.findall(r"a(\d+?)","a23b")
# 非贪婪模式

['2']

>>> re.findall(r"a(\d+)","a23b")

['23']

注意比较这种情况：

>>> re.findall(r"a(\d+)b","a23b")

['23']

>>> re.findall(r"a(\d+?)b","a23b")
#如果前后均有限定条件，则非匹配模式失效

['23']

2 如果你要多行匹配，那么加上re.S和re.M标志

re.S：.将会匹配换行符，默认.逗号不会匹配换行符

>>> re.findall(r"a(\d+)b.+a(\d+)b","a23b\na34b")

[]

>>> re.findall(r"a(\d+)b.+a(\d+)b","a23b\na34b",re.S)

[('23','34')]

>>>

re.M：^$标志将会匹配每一行，默认^只会匹配符合正则的第一行；默认$只会匹配符合正则的末行

>>> re.findall(r"^a(\d+)b","a23b\na34b")

['23']

>>> re.findall(r"^a(\d+)b","a23b\na34b",re.M)

['23','34']

但是，如果没有^标志，

>>> re.findall(r"a(\d+)b","a23b\na34b")

['23','43']

可见，是无需re.M

import re

n='''12 drummers drumming,

11 pipers piping, 10 lords a-leaping'''

p=re.compile('^\d+')

p_multi=re.compile('^\d+',re.MULTILINE) #设置 MULTILINE 标志

print re.findall(p,n) #['12']

print re.findall(p_multi,n) # ['12', '11']

============================

import re

a = 'a23b'

print re.findall('a(\d+?)',a) #['2']

print re.findall('a(\d+)',a) #['23']

print re.findall(r'a(\d+)b',a) #['23']

print re.findall(r'a(\d+?)b',a) # ['23']

============================

b='a23b\na34b'

''' . 匹配非换行符的任意一个字符'''

print re.findall(r'a(\d+)b.+a(\d+)b',b) #[]

print re.findall(r'a(\d+)b',b,re.M) # ['23', '34']

print re.findall(r'^a(\d+)b',b,re.M) # ['23', '34']

print re.findall(r'a(\d+)b',b) #['23','34'] 可以匹配多行

print re.findall(r'^a(\d+)b',b) # ['23'] 默认^只会匹配符合正则的第一行

print re.findall(r'a(\d+)b$',b) # ['34'] 默认$只会匹配符合正则的末行

print re.findall(r'a(\d+)b',b,re.M) #['23', '34']

print re.findall(r'a(\d+)b.?',b,re.M) # ['23', '34']

print re.findall(r"a(\d+)b", "a23b\na34b") # ['23', '34']

============================