Replace all occurances of a number in a matrix python

Question

The input is a multi-line string containing the matrix:

input = '''22 13 17 11  0
 8  2 23  4 24
21  9  7 16  7
 6 10  3  7  5
 1 12 20 15 19'''

I have to replace all the occurrences of, let's say 7 with -1. So the output array would be:

output = '''22 13 17 11  0
 8  2 23  4 24
21  9  -1 16  -1
 6 10  3  -1  5
 1 12 20 15 19'''

Answer 1

You could keep it in string format and simply use a word-separator regex and sub all the specific numbers you want:

import re

s = '''22 13 17 11  0
 8  2 23  4 24
21  9  7 16  7
 6 10  3  7  5
 1 12 20 15 19'''

num = 7
target = -1
print(re.sub(rf'\b{num}\b', str(target), s))

Will give:

22 13 17 11  0
 8  2 23  4 24
21  9  -1 16  -1
 6 10  3  -1  5
 1 12 20 15 19