AttributeError: 'function' object has no attribute 'replace'

I'm using this code to try to replace a character:

from another_test import test_once_more
test_once_more()
question = input("1 letter ")
for letter in question:
    if letter == "a":
        test_once_more.replace("1","a")
        print (test_once_more)

This is the code I am using. All I want it to do is replace the 1 in this code.

def test_once_more():
    print ("123456789")

and replace it with an "A"

You can't.

The function is printing something and returns None. There's no way to change that after the fact.

What you should do is have the function return a value and work on that:

def test_once_more():
    return "123456789"

and then

from another_test import test_once_more
result = test_once_more()
question = input("1 letter ")
for letter in question:
    if letter == "a":
        result = result.replace("1","a")
        print (result)

although I'm puzzled why you're using a for loop to iterate over a string that will be a single character (at least if your user follows your request)...