Auto activating a python virtualenv

activate.py

from subprocess import run
from os import path, getenv
import sys

DEBUG = getenv('DEBUG', False)

def get_base_prefix_compat():
    """Get base/real prefix, or sys.prefix if there is none."""
    return (
        getattr(sys, "base_prefix", None)
        or getattr(sys, "real_prefix", None)
        or sys.prefix
    )

def in_virtualenv():
    print(f" sys.prefix: {sys.prefix}\nbase_prefix: {get_base_prefix_compat()}") if DEBUG else None
    return sys.prefix != get_base_prefix_compat()

def activate(env_name, python_ver = f"python{sys.version_info.major}.{sys.version_info.minor}"):
    if not in_virtualenv():
        pyactivate_path = path.abspath(path.join(path.dirname(__file__),
            env_name,
            "bin",
            "activate"))
        pypath = path.abspath(path.join(path.dirname(__file__),
            env_name,
            "lib",
            python_ver,
            "site-packages"))
        try:
            print(f"source {pyactivate_path}") if DEBUG else None
            run(f"source {pyactivate_path}", shell = True)
            print(f"Prepending to path: {pypath}") if DEBUG else None
            sys.path.insert(0, pypath)
        except Exception as e:
            print(f"Error activating virtual environment: {e}")
            sys.exit(1)

my_script.py

#!/usr/bin/env python3
''' A quick script that just does nothing - just to show this off
    Shows off single parameter call
'''

# Need to do this first so you will find your modules
from activate import activate
activate(".venv")         # First param is the virtualenv directory, second optional param is the python version
import simple_term_menu   # Import virtualenv modules

if __name__ == __main__:
  print("Here I am")

my_script2.py

#!/usr/bin/env python3
''' A quick script that just does nothing - just to show this off.
    Shows off 2 parameters call
'''

# Need to do this first so you will find your modules
from activate import activate
activate(".venv", "python3.13") # First param is the virtualenv directory, second optional param is the python version
import simple_term_menu         # Import virtualenv modules

if __name__ == __main__:
  print("Here I am")

Some people exist an example of what NOT to do.
Don't do this gumph.

Use uv instead
https://docs.astral.sh/uv/guides/scripts/#declaring-script-dependencies