trying to edit a text file

[menator01]

Maybe something like this:

#! /usr/bin/env python3

import re
file = 'some.txt'

mylist = []
with open(file, 'r') as lines:
    print('----Original----')
    for line in lines:
        print(line.strip())
        new_line = re.sub('whiff', 'woo', line)
        mylist.append(new_line)

with open(file, 'w') as lines:
    for line in mylist:
        lines.write(f'{line.strip()}\n')

with open(file, 'r') as lines:
    print()
    print('----New File----')
    for line in lines:
        print(line.strip())

Output:
----Original----
yippe
wahoo
whiffenhard
yerp

----New File----
yippe
wahoo
wooenhard
yerp