Python command line tool with subcommands in typer - How do I include a Typer instance with only one command?

Question

When writing a command line tool in Python using Typer one can create a CLI with commands and even subcommands. If you define a CLI with only one command the CLI will be optimized such that you do not have to provide the command - let's call this modul cli_a.py:

#!env python

import typer

app = typer.Typer()

@app.command()
def main():
    print('This is the output of main')

if __name__ == '__main__':
    app()

Now, you can call this CLI like so

$ ./cli_a.py --help

 Usage: cli_a.py [OPTIONS]

╭─ Options ───────────────────────────────────────────────────────────────────╮
│ --install-completion          Install completion for the current shell.     │
│ --show-completion             Show completion for the current shell, to     │
│                               copy it or customize the installation.        │
│ --help                        Show this message and exit.                   │
╰─────────────────────────────────────────────────────────────────────────────╯

and

$ ./cli_a.py 
This is the output of main

Notice, that there has to be no command called main!

On the other hand you can have a CLI with multiple commands - let's call this cli_b.py:

#!env python
import typer

app = typer.Typer()

@app.command()
def cmd1():
    print('This is the output of cmd1')

@app.command()
def cmd2():
    print('This is the output of cmd2')

if __name__ == '__main__':
    app()

With the following output:

$ ./cli_b.py --help

 Usage: cli_b.py [OPTIONS] COMMAND [ARGS]...

╭─ Options ───────────────────────────────────────────────────────────────────╮
│ --install-completion          Install completion for the current shell.     │
│ --show-completion             Show completion for the current shell, to     │
│                               copy it or customize the installation.        │
│ --help                        Show this message and exit.                   │
╰─────────────────────────────────────────────────────────────────────────────╯
╭─ Commands ──────────────────────────────────────────────────────────────────╮
│ cmd1                                                                        │
│ cmd2                                                                        │
╰─────────────────────────────────────────────────────────────────────────────╯

In this case you have to provide the command to be called:

$ ./cli_b.py cmd1
This is the output of cmd1

I want to combine these two CLI into one - let's call this super_cli.py:

#!env python
import typer
import cli_a
import cli_b

app = typer.Typer()
app.add_typer(cli_a.app, name='cli_a')
app.add_typer(cli_b.app, name='cli_b')

if __name__ == '__main__':
    app()

This behaves as expected for cli_b:

$ ./super_cli.py cli_b cmd1
This is the output of cmd1

But requires an unwanted additional command main on cli_a:

$ ./super_cli.py cli_a main
This is the output of main

How can it be achieved that cli_a is callable without specifying the additional command main?

I was expecting to get

$ ./super_cli.py cli_a
This is the output of main

but I do get

$ ./super_cli.py cli_a
Usage: super_cli.py cli_a [OPTIONS] COMMAND [ARGS]...
Try 'super_cli.py cli_a --help' for help.
╭─ Error ─────────────────────────────────────────────────────────────────────╮
│ Missing command.                                                            │
╰─────────────────────────────────────────────────────────────────────────────╯

instead.

using Google to search typer default command I found Set the default command in Python Typer CLI — furas
– furas, Commented Mar 6 at 2:54

furas · Accepted Answer · 2025-03-06 03:21:06Z

0

Searching typer default command in Google I found:
Set the default command in Python Typer CLI

You need to change command() into callback(invoke_without_command=True) in cli_a.py and it will treat main() as default command.

import typer

app = typer.Typer()

@app.callback(invoke_without_command=True)
def main():
    print('This is the output of main')

if __name__ == '__main__':
    app()

And now ./super_cli cli_a runs cli_a.main()

Executing directly ./cli_a.py still work as before.

I used callback() on cmd1 in cli_b

import typer

app = typer.Typer()

@app.callback(invoke_without_command=True)
def cmd1():
    print('This is the output of cmd1')

@app.command()
def cmd2():
    print('This is the output of cmd2')

if __name__ == '__main__':
    app()

and it was running cmd1 automatically for super_cli.py cli_b BUT it was running it autmatically also for super_cli.py cli_b cmd2 :)

$ ./super_cli.py cli_b

This is the output of cmd1


$ ./super_cli.py cli_b cmd2

This is the output of cmd1
This is the output of cmd2

Some links to documentation:

edited Mar 6 at 3:21

answered Mar 6 at 3:07

furas

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2 Comments

Andre Alexander Bell Mar 6 at 13:52

Thanks for your answer. I do use callbacks to add in help and options available accross all commands of one cli. However, what I am not happy about is that extending a cli with a second command at some later point in time requires to refactor the callback back into a command.

furas Mar 6 at 14:26

I don't remeber if I tried to run script (which has only one function) using only callback. If it would work then you could always use callback for first function. OR I would always add both command() and callback() but callback in comment - so it would be simpler to replace it when I would add second function. Other idea: check source code to see how it works when script has only one function. But this can be hard job. I wonder if it could be possible to use some if/else which would add differen decorators if code has more functions. Some decorators can be used like functions.

MCFreddie777 · Accepted Answer · 2025-09-24 22:39:02Z

0

Also, if you want to do something different when the subcommand is called without any other argument, use ctx.invoked_subcommand

import subprocess
import typer

app = typer.Typer()

@app.callback(invoke_without_command=True)
def main(ctx: typer.Context):
    """Seed the database with default data."""
    if ctx.invoked_subcommand is None:
        print("Seeding all the data...")

@app.command()
def clients() -> None:
    """Seed the clients"""
    print("Seeding clients...")


if __name__ == "__main__":
    app()

answered Sep 24 at 22:39

MCFreddie777

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