My script:

#!/usr/bin/env python
import pathlib
import subprocess

output = subprocess.check_output(['ps', 'aux'])
pathlib.Path('/tmp/ps_aux.txt').write_bytes(output)


When I execute the following script in the REPL, I get your issue but for me, it's normal because the REPL is running in a terminal with a limited size. 

And when I execute the same script like as a simple python script, I don't have your issue.