Python regex replace each match with itself plus a new line

Question

I have a long regex with many alternations and I want to be able to replace each match from the regex with itself followed by a new line ('\n').

What is the most efficient way to do so with re.sub()?

Here is a simple example:

s = 'I want to be able to replace many words, especially in this sentence, since it will help me solve by problem. That makes sense right?'

pattern = re.compile(r'words[,]|sentence[,]|problem[.]')

for match in matches:
    re.sub(pattern, match + '\n', match)

I know this for loop will not work, I am just hoping to clarify what I am trying to solve here. Thanks in advance for any help. I may be missing something very straightforward.

Ok will do. Is there not a simple way to iterate through each match object and replace it with itself plus a newline character? I'm not sure if Python can translate between match objects and strings, which may be the problem. — rahlf23
– rahlf23, Commented Sep 18, 2017 at 22:54
That is what I would like to do I guess. I have five different matching options in one regex formula for identifying the ends of sentences (for my specific application) and I would just like to replace each match that it finds with itself plus a newline character. I only have one capturing group, which would be the full matches themselves. — rahlf23
– rahlf23, Commented Sep 18, 2017 at 22:57

Wiktor Stribiżew · Accepted Answer · 2017-09-19 06:15:33Z

To replace a whole match with itself you may use a replacement backreference \g<0>. However, you want to replace and store the matches inside a variable. You need to pass a callback method as a replacement argument to re.sub, and return the whole match value (match.group()) with a newline appended to the value:

import re
matches = []                          # Variable to hold the matches
def repl(m):                          # m is a match data object
    matches.append(m.group())         # Add a whole match value
    return "{}\n".format(m.group())   # Return the match and a newline appended to it

s = 'I want to be able to replace many words, especially in this sentence, since it will help me solve by problem. That makes sense right?'
pattern = re.compile(r'words[,]|sentence[,]|problem[.]')
s = re.sub(pattern, repl, s)

print(s)
print(matches)

See the Python demo

Otobong Jerome · Accepted Answer · 2021-01-15 14:29:10Z

1

the second parameter of re.sub can either be a string or a callable that takes in the match instance and returns a string. so do this

def break_line(match):
    return "\n" + match.group()

text = re.sub(pattern, break_line, text)

answered Jan 15, 2021 at 14:29

Otobong Jerome

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Comments

cclsr · Accepted Answer · 2017-09-19 02:06:50Z

0

Just like this?

    text ='I want to be able to replace many words, especially in this sentence, since it will help me solve by problem. That makes sense right?'
    text_list = tex t.replace('.',',').strip(',|.|?').split(',')
    ##Remove the beginning and end symbols.And split by ','
    print (text_list)
    for i in text_list:
        ii=i.split(',')
        print(ii)

Result

    ['I want to be able to replace many words', ' especially in this sentence', ' since it will help me solve by problem', ' That makes sense right']
    ['I want to be able to replace many words']
    [' especially in this sentence']
    [' since it will help me solve by problem']
    [' That makes sense right']

answered Sep 19, 2017 at 2:06

cclsr

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1 Comment

cclsr Over a year ago

text_list = re.sub(r'[,.?]+',',',text).strip(',').split(',')

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