Add text 2 lines before match in python

Question

I am trying to find "AAXX" and add the word "Hello" two lines above:

Input:
111
222
AAXX
333
444
AAXX
555
666
AAXX

Output: 
Hello 
111
222
AAXX
Hello
333 
444
AAXX
Hello
555
666
AAXX

I have managed to insert only one "Hello" two lines before the first "AAXX" by using the code below, but I cannot make it loop through the file and do the same for all "AAXX" matches.

import os

with open(os.path.expanduser("~/Desktop/test.txt"), "r+") as f:
    a = [x.rstrip() for x in f]
    for i, item in enumerate(a):
        if item.startswith("AAXX"):
            a.insert(i-2,"Hello")
            break
        index += 1
    # Go to start of file and clear it
    f.seek(0)
    f.truncate()
    # Write each line back
    for line in a:
        f.write(line + "\n")

So far, I get:

Hello
111
222
AAXX
333
444
AAXX
555
666
AAXX

Answer 1

Can you try the following:

with open('test.txt', 'r') as infile:
    data = infile.read()
final_list = []
for ind, val in enumerate(data.split('\n')):
    final_list.append(val)
    if val == 'AAXX':
        final_list.insert(-3, 'HELLO')
# save the text file
with open('test.txt', 'w') as outfile:
    data = outfile.write('\n'.join(final_list))

Output:

HELLO
111
222
AAXX
HELLO
333
444
AAXX
HELLO
555
666
AAXX