如何在string.replace中输入正则表达式？

Question

我需要一些关于声明正则表达式的帮助.我的输入如下:

this is a paragraph with<[1> in between</[1> and then there are cases ... where the<[99> number ranges from 1-100</[99>. 
and there are many other lines in the txt files
with<[3> such tags </[3>

所需的输出是:

this is a paragraph with in between and then there are cases ... where the number ranges from 1-100. 
and there are many other lines in the txt files
with such tags

我试过这个:

#!/usr/bin/python
import os, sys, re, glob
for infile in glob.glob(os.path.join(os.getcwd(), '*.txt')):
    for line in reader: 
        line2 = line.replace('<[1> ', '')
        line = line2.replace('</[1> ', '')
        line2 = line.replace('<[1>', '')
        line = line2.replace('</[1>', '')

        print line

我也尝试了这个(但似乎我使用了错误的正则表达式语法):

    line2 = line.replace('<[*> ', '')
    line = line2.replace('</[*> ', '')
    line2 = line.replace('<[*>', '')
    line = line2.replace('</[*>', '')

我不想硬编码replace从1到99...

Answer 1

这个经过测试的代码片段应该这样做:

import re
line = re.sub(r"</?\[\d+>", "", line)

编辑:这是一个注释版本,解释它是如何工作的:

line = re.sub(r"""
  (?x) # Use free-spacing mode.
  <    # Match a literal '<'
  /?   # Optionally match a '/'
  \[   # Match a literal '['
  \d+  # Match one or more digits
  >    # Match a literal '>'
  """, "", line)

正则表达很有趣!但我强烈建议花一两个小时研究基础知识.对于初学者,你需要了解哪些字符是特殊的:"元字符"需要被转义(即在前面放置一个反斜杠 - 规则在字符类内外都不同.)有一个很好的在线教程:www .regular-expressions.info.你在那里度过的时间会多次为自己付出代价.快乐regexing!

Answer 2

str.replace()固定替换.请re.sub()改用.

Answer 3

我会这样(正则表达式在评论中解释):

import re

# If you need to use the regex more than once it is suggested to compile it.
pattern = re.compile(r"</{0,}\[\d+>")

# <\/{0,}\[\d+>
# 
# Match the character “<” literally «<»
# Match the character “/” literally «\/{0,}»
#    Between zero and unlimited times, as many times as possible, giving back as needed (greedy) «{0,}»
# Match the character “[” literally «\[»
# Match a single digit 0..9 «\d+»
#    Between one and unlimited times, as many times as possible, giving back as needed (greedy) «+»
# Match the character “>” literally «>»

subject = """this is a paragraph with<[1> in between</[1> and then there are cases ... where the<[99> number ranges from 1-100</[99>. 
and there are many other lines in the txt files
with<[3> such tags </[3>"""

result = pattern.sub("", subject)

print(result)

如果您想了解有关正则表达式的更多信息,我建议您阅读Jan Goyvaerts和Steven Levithan撰写的正则表达式食谱.

Answer 4

最简单的方法

import re

txt='this is a paragraph with<[1> in between</[1> and then there are cases ... where the<[99> number ranges from 1-100</[99>.  and there are many other lines in the txt files with<[3> such tags </[3>'

out = re.sub("(<[^>]+>)", '', txt)
print out

Answer 5

替换字符串对象的方法不接受正则表达式,只接受固定字符串(参见文档:http://docs.python.org/2/library/stdtypes.html#str.replace).

你必须使用re模块:

import re
newline= re.sub("<\/?\[[0-9]+>", "", line)

Answer 6

不必使用正则表达式（对于您的示例字符串）

>>> s
'this is a paragraph with<[1> in between</[1> and then there are cases ... where the<[99> number ranges from 1-100</[99>. \nand there are many other lines in the txt files\nwith<[3> such tags </[3>\n'

>>> for w in s.split(">"):
...   if "<" in w:
...      print w.split("<")[0]
...
this is a paragraph with
 in between
 and then there are cases ... where the
 number ranges from 1-100
.
and there are many other lines in the txt files
with
 such tags