How to add arguments to Python script entrypoint based on conditions

Question

I have an entry point like so:

ENTRYPOINT [ "python" ,"/usr/local/bin/script.py" ]

I want to be able to add multiple arguments to script.py if a particular container has "MY_ENV_VAR" set to TRUE.

So for instance if:

MY_ENV_VAR = true
MY_ENV_VAR2 = true
MY_ENV_VAR3 = false (or anything other than true)

I want to run /usr/local/bin/script.py --my-env-var --my-env-var2

I can't find a good working example of how to accomplish this

You can't configure the ENTRYPOINT to change according to whether an env var is present or not, but you can make it so that the `script.py` prompts you with the right options by using argparse properly — Paolo, Mar 16 '22 at 16:39
Another approach would be to-- use the ENV inside your script.py and do conditional stmt based on ENV. — Gupta, Mar 16 '22 at 16:54
[Setting options from environment variables when using argparse](https://stackoverflow.com/questions/10551117/setting-options-from-environment-variables-when-using-argparse) describes a generic approach for doing this (setting `default=os.environ['MY_ENV_VAR']` for each option in your `argparse` configuration); this will translate just fine to Docker without changing anything. Does that setup work for you? — David Maze, Mar 16 '22 at 16:58

Paolo · Answer 1 · 2022-03-16T22:18:27.897

You will not be able to conditionally do this within the Dockerfile, but you can achieve the desired behavior by configuring the Python script script.py as follows:

import argparse
import os

def main():
    parser = argparse.ArgumentParser("Arguments")

    if os.environ.get("MY_ENV_VAR") is not None:
        parser.add_argument("--my-env-var", required=True, action="store_true")
    
    if os.environ.get("MY_ENV_VAR2") is not None:
        parser.add_argument("--my-env-var2", required=True, action="store_true")
    
    parser.parse_args()

if __name__ == "__main__":
    main()

The logic is that if MY_ENV_VAR or MY_ENV_VAR2, then a required argparse argument is set.

How to add arguments to Python script entrypoint based on conditions

1 Answers1