erhan erhan - 1 month ago 12
Python Question

how to replace a line of two words in a file using python

I want to replace a line in a file but my code doesn't do what I want. The code doesn't change that line. It seems that the problem is the space between ALS and 4277 characters in the input.txt. I need to keep that space in the file. How can I fix my code?

A part part of input.txt:

ALS 4277


Related part of the code:

for lines in fileinput.input('input.txt', inplace=True):
print(lines.rstrip().replace("ALS"+str(4277), "KLM" + str(4945)))


Desired output:

KLM 4945

Answer

As the spaces vary you will need to use regex to account for the spaces.

import re

lines = "ALS              4277    "
line = re.sub(r"(ALS\s+4277)", "KLM              4945", lines.rstrip())

print(line)
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