How to determine if Python script was run using typer?

I want to change the behaviour of a function based on whether it was normally called or called via typer command line program...

from typer import Typer

app = typer.Typer()

@app.command()
def do(a, b, c):
   output = a+b+c
   if <invoked via typer app>:
      print(output)
   return output

if __name__ == '__main__':
   app()

What would the right thing be in place of <invoiked via typer app> above?

Via app.callback()

It can be solved by setting a global or environment variable but it feels like a hack

I'm not the biggest fan of this solution myself as it also kind of pollutes the function signature, however you can achieve it by adding the Context like so:

from typer import Typer, Context

app = Typer()


@app.command()
def do(
    a,
    b,
    c,
    ctx: Context = None,  # type: ignore
):
    output = a + b + c
    if ctx:
        print(output)
    return output


if __name__ == "__main__":
    app()

Read more about its intended uses here https://typer.tiangolo.com/tutorial/commands/context/