I would like to emphasize an answer that was in the comments that is working well for me. As mikey has said, this will work if you want to have variables in the included file in scope in the caller of 'include', just insert it as normal python. It works like an include statement in PHP. Works in Python 3.8.5. Happy coding!
Alternative #1
import textwrap
from pathlib import Path
exec(textwrap.dedent(Path('myfile.py').read_text()))
Alternative #2
with open('myfile.py') as f: exec(f.read())