使用ReGex匹配表达式，Python [英] Matching an expression using ReGex ,Python

问题描述

我有很多句子，尽管我会创建一个可以对每个句子单独操作的函数.所以输入只是一个字符串.我的主要目标是提取像"near blue meadows"这样的介词之后的单词，我希望提取blue meadows.
我所有的介词都放在一个文本文件中.它工作正常，但我想所用的正则表达式存在问题.这是我的代码: 汇入

I have many sentences , though i'd create a function that would operate on each sentence individually. so the input is just a string. My main objective is to extract the words that follow prepositions like in "near blue meadows" i'd want blue meadows to be extracted.
I have all my prepositions in a text file. it works fine but i guess there's a problem in the regex used . here's my code: import re

with open("Input.txt") as f:
    words = "|".join(line.rstrip() for line in f)
    pattern = re.compile('({})\s(\d+\w+|\w+)\s\w+'.format(words))
    text3 = "003 canopy grace appt, classic royale garden, hennur main road, bangalore 43. near hennur police station"
    print(pattern.search(text3).group())

这将返回:

AttributeError                            Traceback (most recent call last)
<ipython-input-83-be0cdffb436b> in <module>()
      5     pattern = re.compile('({})\s(\d+\w+|\w+)\s\w+'.format(words))
      6     text3 = ""
----> 7     print(pattern.search(text3).group())

AttributeError: 'NoneType' object has no attribute 'group

主要问题是使用正则表达式，我的预期输出是"hennur警察"，即near后2个字.在我的代码中，我使用了({})来匹配准备列表，其中\s之后是空格，(\d+\w+|\w+)之后是19th或hennur之类的单词，\s\w+之后是一个空格和一个单词.我的正则表达式无法匹配，因此出现了None错误. 为什么它不起作用?

The main problem is with regex , my expected output is "hennur police" i.e 2 words after near . In my code I have used ({}) to match from the list of preps, \s followed by space , (\d+\w+|\w+) followed by words like 19th or hennur , \s\w+ followed by a space and a word. My regex fails to match , hence the None error. Why is it not working?

Input.txt文件的内容:

The content of the Input.txt file:

['near','nr','opp','opposite','behind','towards','above','off']

预期输出:

hennur police

推荐答案

该文件包含Python列表文字.使用 ast.literal 来解析文字.

The file contains Python list literal. Use ast.literal to parse the literal.

>>> import ast
>>> ast.literal_eval("['near','nr','opp','opposite','behind','towards','above','off']")
['near', 'nr', 'opp', 'opposite', 'behind', 'towards', 'above', 'off']

---

import ast
import re

with open("Input.txt") as f:
    words = '|'.join(ast.literal_eval(f.read()))
    pattern = re.compile('(?:{})\s(\d*\w+\s\w+)'.format(words))
    text3 = "003 canopy grace appt, classic royale garden, hennur main road, bangalore 43. near hennur police station"

    # If there could be multiple matches, use `findall` or `finditer`
    #   `findall` returns a list of list if there's capturing group instead of
    #   entire matched string.
    for place in pattern.findall(text3):
        print(place)

    # If you want to get only the first match, use `search`.
    #   You need to use `group(1)` to get only group 1.
    print pattern.search(text3).group(1)

输出(第一行以for循环打印，第二行来自search(..).group(1)):

output (The first line is printed in for loop, the second one come from search(..).group(1)):

hennur police
hennur police

注意，您需要 re.escape 每个单词，如果该单词中有任何特殊字符在正则表达式中具有特殊含义.

NOTE you need to re.escape each word if there's any special character in the word that has special meaning in regular expression.

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