what is the way to replace a line in a file using python

Question

I want to replace a line in a text file using Python. Basically I am looping over a file and when I find a relevant line that needs to be replaced, I want to replace it at the same position in the file.

Can this be done in Python without creating a completely new file?

unutbu · Accepted Answer · 2013-07-30T20:43:58.693

3

I like using the fileinput module for this. It has an option for making a backup file, and it preserves permissions.

import fileinput
import sys

for line in fileinput.input([filename], inplace=True):
    if condition:
        sys.stdout.write(newline)
    else:
        sys.stdout.write(line)

This does create a new (temporary) file, then renames that file to filename, so the change appears to be in-place.

edited Jul 30 '13 at 20:43

answered Jul 30 '13 at 20:26

unutbu

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It gives me this error sys.write(finallog) AttributeError: 'module' object has no attribute 'write' – Saurabh Jul 30 '13 at 20:43
Sorry, `sys.write` should have been `sys.stdout.write`. – unutbu Jul 30 '13 at 20:44

what is the way to replace a line in a file using python

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