Question

python 正则表达式，如下数字8.5如何提取？

在字符串[u'\n 8.5\n '] 中提取数字
thx

Answer 1

>>> src = ur"""
...     8.5   
... """
>>> src
u'\n    8.5   \n'
>>> import re
>>> patt = re.compile(r"(\d+\.\d+)")
>>> patt.findall(src)
[u'8.5']
>>>

追问

　　其实我的应用场景是爬虫，提取豆瓣的书籍评分

　　

　　但是这个结果就是空

　　我只能把(\d+\.\d+) 换成(.*?) 但是结果又是'\n    8.5   \n'

　　请问为什么(\d+\.\d+)结果是空？谢谢

追答

Help on function search in module re:

search(pattern, string, flags=0)
    Scan through string looking for a match to the pattern, returning
    a match object, or None if no match was found.

findall(pattern, string, flags=0)
    Return a list of all non-overlapping matches in the string.
    
    If one or more groups are present in the pattern, return a
    list of groups; this will be a list of tuples if the pattern
    has more than one group.
    
    Empty matches are included in the result.
(END)

Example:

>>> context = ur"""
...     8.5   
... """
>>> context
u'\n    8.5   \n'
>>> patt = re.compile(r"(\d+\.\d+)")
>>> m = patt.search(context)
>>> m.group()
u'8.5'
>>> f = patt.findall(context)
>>> f
[u'8.5']
>>>