Application that prints to STDOUT and STDERR

import sys

def welcome(to_out, to_err=None):
    print(f"STDOUT: {to_out}")
    if to_err:
        print(f"STDERR: {to_err}", file=sys.stderr)

from greet import welcome

welcome("Jane", "Joe")
print('---')
welcome("Becky")

Output:

STDERR: Joe
STDOUT: Jane
---
STDOUT: Becky