re.findall 行为怪异

问题描述

源字符串是:

# Python 3.4.3
s = r'abc123d, hello 3.1415926, this is my book'

这是我的模式:

pattern = r'-?[0-9]+(\.[0-9]*)?|-?\.[0-9]+'

但是，re.search 可以给我正确的结果:

however, re.search can give me correct result:

m = re.search(pattern, s)
print(m)  # output: <_sre.SRE_Match object; span=(3, 6), match='123'>

re.findall 只是转储一个空列表:

re.findall just dump out an empty list:

L = re.findall(pattern, s)
print(L)  # output: ['', '', '']

为什么不能 re.findall 给我预期的列表:

why can't re.findall give me the expected list:

['123', '3.1415926']

推荐答案

s = r'abc123d, hello 3.1415926, this is my book'
print re.findall(r'-?[0-9]+(?:.[0-9]*)?|-?.[0-9]+',s)

您在使用原始模式时不需要转义两次.

You dont need to escape twice when you are using raw mode.

输出:['123', '3.1415926']

返回类型也是字符串的列表.如果您希望返回类型为 integers 和 floats，请使用 map

Also the return type will be a list of strings. If you want return type as integers and floats use map

import re,ast
s = r'abc123d, hello 3.1415926, this is my book'
print map(ast.literal_eval,re.findall(r'-?[0-9]+(?:.[0-9]*)?|-?.[0-9]+',s))

输出:[123, 3.1415926]

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