我试图提取所有含有从文本指定单词的句子。
txt="I like to eat apple. Me too. Let's go buy some apples."
txt = "." + txt
re.findall(r"\."+".+"+"apple"+".+"+"\.", txt)
但它返回我：
[".I like to eat apple. Me too. Let's go buy some apples."]
代替 ：
[".I like to eat apple., "Let's go buy some apples."]
任何帮助吗？
In [3]: re.findall(r"([^.]*?apple[^.]*\.)",txt)
Out[4]: ['I like to eat apple.', " Let's go buy some apples."]
无需正则表达式：
>>> txt = "I like to eat apple. Me too. Let's go buy some apples."
>>> [sentence + '.' for sentence in txt.split('.') if 'apple' in sentence]
['I like to eat apple.', " Let's go buy some apples."]
In [7]: import re
In [8]: txt=".I like to eat apple. Me too. Let's go buy some apples."
In [9]: re.findall(r'([^.]*apple[^.]*)', txt)
Out[9]: ['I like to eat apple', " Let's go buy some apples"]
但是请注意，@ jamylak的split为基础的解决方案是快：
In [10]: %timeit re.findall(r'([^.]*apple[^.]*)', txt)
1000000 loops, best of 3: 1.96 us per loop
In [11]: %timeit [s+ '.' for s in txt.split('.') if 'apple' in s]
1000000 loops, best of 3: 819 ns per loop
该速度差较小，但仍然显著，对于较大的字符串：
In [24]: txt = txt*10000
In [25]: %timeit re.findall(r'([^.]*apple[^.]*)', txt)
100 loops, best of 3: 8.49 ms per loop
In [26]: %timeit [s+'.' for s in txt.split('.') if 'apple' in s]
100 loops, best of 3: 6.35 ms per loop
您可以使用str.split ，
>>> txt="I like to eat apple. Me too. Let's go buy some apples."
>>> txt.split('. ')
['I like to eat apple', 'Me too', "Let's go buy some apples."]
>>> [ t for t in txt.split('. ') if 'apple' in t]
['I like to eat apple', "Let's go buy some apples."]
r"\."+".+"+"apple"+".+"+"\."
这条线是有点奇怪; 为什么拼接这么多不同的字符串？ 你可以只使用R '.. +苹果+'。
无论如何，你的正则表达式的问题是其贪婪的烦躁。 默认情况下， x+将匹配x经常因为它可能可以。 所以，你的.+将匹配尽可能多的字符（ 任何字符）成为可能; 包括点和apple秒。
要改用什么是是非贪婪的表达; 你通常可以通过添加一个做到这一点? 结尾： .+? 。
这会让你得到以下结果：
['.I like to eat apple. Me too.']
正如你所看到的你不再同时获得苹果的句子，但仍是Me too. 。 那是因为你仍然匹配. 在之后apple ，使得它不可能没有捕捉到下面的句子也是如此。
一个工作正则表达式将是这样的： r'\.[^.]*?apple[^.]*?\.'
在这里，你不看任何字符，但只有那些不是字符圆点自己。 我们也允许不匹配的所有任何字符（因为之后apple在第一个句子中没有任何不点的字符）。 使用本该表达式的结果：
['.I like to eat apple.', ". Let's go buy some apples."]
很显然，有问题的样本extract sentence containing substring ，而不是
extract sentence containing word 。 如何解决extract sentence containing word通过蟒蛇的问题如下：
一个字可以在开始时|中|句末。 不限于问题的例子，我将提供一个句子中搜索词的一般功能：
def searchWordinSentence(word,sentence):
pattern = re.compile(' '+word+' |^'+word+' | '+word+' $')
if re.search(pattern,sentence):
return True
限于问题的例子，我们可以解决这样的：
txt="I like to eat apple. Me too. Let's go buy some apples."
word = "apple"
print [ t for t in txt.split('. ') if searchWordofSentence(word,t)]
相应的输出是：
['I like to eat apple']
