Take user input and split files using 7z in python

[snippsat]

Do not use os.system subprocess has taken over that task long ago.
cd in a subprocess use cwd argument to change directory.
Working example that spilt up rain.mp3 in 2-mb files and place files in C:\code.

import subprocess

intput_file = 'rain.mp3'
output_files = 'rain_a.7z'
subprocess.run([r'C:\Program Files\7-Zip\7z.exe', 'a', '-v2m', output_files, intput_file], cwd=r'C:\code')