Python正则表达式仅根据正则表达式替换段落中的特定行而不是整个文件

Posted 2023-03-28

【中文标题】Python正则表达式仅根据正则表达式替换段落中的特定行而不是整个文件

【英文标题】：Python regex to replace a Particular line in paragraphs as per regex only not whole file

【发布时间】：2021-09-06 15:58:30

【问题描述】：

s="""Paragraph 1
some text blah blah
blah blah
UNWANTED TEXT
some text
Paragraph END

UNWNTED TEXT

Paragraph 2
some text blah blah
blah blah
UNWNTED TEXT
Paragraph END"""

现在 python 代码 re.sub 以仅在段落内替换 UNWANTED TEXT 保留 UNWANTED TEXT 在段落外

search_unwanted_only_inparagrap = re.findall('(?s)(?<=Paragraph)(.*?)(?=END)', text_file, flags = re.MULTILINE )
if search_unwanted_only_inparagrap:
    replace_only_insidepara = re.sub(r"UNWANTED TEXT+", " ", text_file)   #replace string substitue
    print (replace_only_insidepara)
else:
    print ("not found")    

但是输出替换了文件中所有 UNWANTED TEXT 的实例

Paragraph 1
some text blah blah
blah blah

some text
Paragraph END



Paragraph 2
some text blah blah
blah blah

Paragraph END

但我希望这样

Paragraph 1
some text blah blah
blah blah

some text
Paragraph END

UNWNTED TEXT

Paragraph 2
some text blah blah
blah blah

Paragraph END

请帮忙。

【参考方案1】：

您的演示输入应该更“最少”。但是，我试图了解您的要求并尝试了 re.split 作品：

import re

s = """Paragraph 1
some text blah blah
blah blah
UNWANTED TEXT
some text
Paragraph END

UNWANTED TEXT

Paragraph 2
some text blah blah
blah blah
UNWANTED TEXT
Paragraph END"""
reg_para = re.compile(r'(Paragraph\s+\d+.+?END)', re.DOTALL)
paras = reg_para.split(s)
for para in paras:
    if reg_para.match(para):
        para = re.sub(r"UNWANTED TEXT", " ", para)
        #  in case you want replace more words:
        #  of course you can use list of keywords some loops
        para = re.sub(r"Another WORD", " ", para)
        print(para)
    else:
        print(para)

输出：

Paragraph 1
some text blah blah
blah blah
 
some text
Paragraph END


UNWANTED TEXT


Paragraph 2
some text blah blah
blah blah
 
Paragraph END

【讨论】：

你太棒了。解决了我最近两天一直在苦苦挣扎的问题。非常感谢您宝贵的时间和爱心。

一个额外的查询，我们可以在 re.sub removed = re.sub(r"UNWANTED TEXT", " ", para) 中有多个模式，所有模式只替换空白。喜欢removed = re.sub(r"UNWANTED TEXT", "Another WORD", " ", para)。我已经为整个文本文件使用了 dict 键值对，但是对于这个正则表达式模式需要一些简单的解决方案。谢谢。