python: I want to search a line and replace a line

Question

I want to search a line and replace a line in a file.txt,

CURRENT_BUILD = 111111

with

CURRENT_BUILD = 221111

Using Python.

please show what did you try and what troubles do you have. – Brown Bear Feb 21 '19 at 09:59 — Brown Bear, Feb 21 '19 at 09:59
Is CURRENT_BUILD = 111111 in your txt file – skaul05 Feb 21 '19 at 10:00 — skaul05, Feb 21 '19 at 10:00
Show `file.txt` file content – Alderven Feb 21 '19 at 10:00 — Alderven, Feb 21 '19 at 10:00

score 0 · Accepted Answer · answered Feb 21 '19 at 10:03

0

You can iterate through the lines in the file, saving them to a list and then output the list back to the file, line by line, replacing the line if necessary:

with open('file.txt') as f:
    lines = f.readlines()

with open('file.txt', 'w+') as f:
    for line in lines:
        if line == 'CURRENT_BUILD = 111111\n':
            f.write('CURRENT_BUILD = 221111\n')
        else:
            f.write(line)

answered Feb 21 '19 at 10:03

Sumner Evans

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small change replace line starting with CURRENT_BUILD = with CURRENT_BUILD =555555 – user3664223 Feb 22 '19 at 07:22

K.Madden · Answer 2 · 2019-02-21T10:16:55.953

CURRENT_BUILD = '111111'
print (CURRENT_BUILD.replace('111111', '221111'))

The syntax of replace() is:

str.replace(old, new [, count])

old - old substring you want to replace

new - new substring which would replace the old substring

count (optional) - the number of times you want to replace the old substring with the new substring

If count is not specified, replace() method replaces all occurrences of the old substring with the new substring.

I'm not sure if this is what you meant as you are unclear and haven't shown what the .txt file is but this is replace anyways.

EDIT

if it is in text replace you want then this would be your best bet.

import fileinput

with fileinput.FileInput(filename, inplace=True, backup='.bak') as file:
for line in file:
    print(line.replace(text_to_search, replacement_text), end='')

credit to @jfs from this post How to search and replace text in a file using Python?

python: I want to search a line and replace a line

2 Answers2