[split] Is there some coding that will do the following in 3 separate events?

[Larz60+]

This will read multiple input files and combine into one output file:

import os

# make sure in same directory as source file (you can modify path as desired)
os.chdir(os.path.abspath(os.path.dirname(__file__)))

input_files = ['firstfile.txt', 'secondfile.txt']


for file in input_files:
    with open(file) as fin, open('thirdfile.txt', "a+") as fout:
        fout.write(fin.read())

test:
firstfile.txt:

Output:
Data from first file

secondfile.txt

Output:
Data from second file.

thirdfile.txt:

Output:
Data from first file
Data from second file.

[jefsummers]

In line 5 change the w to an a - as in append. That will then write to the end of the second file.

[bensan]

In line 5 change the w to an a - as in append. That will then write to the end of the second file.

Thanks @jefsummers - The filename (advert) will remain constant so will be no problem there. However, the output_filename will vary because it will be selected by the user (category).

Is there any way the outfile will "write" upon the "user" opening of that file?

[jefsummers]

Sure. The input filename and output filename can be variables