Using regex to replace one number with another of same size in a text file

Question

I have a text file with 100 lines. On each line, there is a number with format nnn.nn .

I have another number NNN.NN . Using Python, I want to replace nnn.nn on each line with NNN.NN . But nnn.nn is located at a different place in the line each time.

I am currently reading in the whole file by:

with open(filename) as f:
    my_file = f.readlines()

and I know that I can find the relevant number by doing:

re.findall(r' \d\d\d.\d\d ',my_file[line_index])[0]

but I'm not sure how to tell my code to replace that number (wherever it is) with my new number.

Answer 1

That would be, also with re:

import re

x="23.320 ododkowe 23.565 odef0oi04 30.403 320"

re.sub(r"\d\d.\d\d\d ", "xx.xxx ", x)

output:

'xx.xxx ododkowe xx.xxx odef0oi04 xx.xxx 320'