Nested SubCommands

We'll now see how these same ideas can be extended for deeply nested commands.

Let's imagine that the same CLI program from the previous examples now needs to handle lands.

But a land could be a reign or town.

And each of those could have their own commands, like create and delete.

A CLI app for reigns

Let's start with a file reigns.py:

import typer

app = typer.Typer()


@app.command()
def conquer(name: str):
    typer.echo(f"Conquering reign: {name}")


@app.command()
def destroy(name: str):
    typer.echo(f"Destroying reign: {name}")


if __name__ == "__main__":
    app()

This is already a simple CLI program to manage reigns:

// Check the help
$ python reigns.py --help

Usage: reigns.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:
  conquer
  destroy

// Try it
$ python reigns.py conquer Cintra

Conquering reign: Cintra

$ python reigns.py destroy Mordor

Destroying reign: Mordor

A CLI app for towns

And now the equivalent for managing towns in towns.py:

import typer

app = typer.Typer()


@app.command()
def found(name: str):
    typer.echo(f"Founding town: {name}")


@app.command()
def burn(name: str):
    typer.echo(f"Burning town: {name}")


if __name__ == "__main__":
    app()

With it, you can manage towns:

// Check the help
$ python towns.py --help

Usage: towns.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:
  burn
  found

// Try it
$ python towns.py found "New Asgard"

Founding town: New Asgard

$ python towns.py burn Vizima

Burning town: Vizima

Manage the land in a CLI app

Now let's put the reigns and towns together in the same CLI program in lands.py:

import typer

import reigns
import towns

app = typer.Typer()
app.add_typer(reigns.app, name="reigns")
app.add_typer(towns.app, name="towns")

if __name__ == "__main__":
    app()

And now we have a single CLI program with a command (or command group) reigns that has its own commands. And another command towns with its own subcommands.

Check it:

// Check the help
$ python lands.py --help

Usage: lands.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:
  reigns
  towns

// We still have the help for reigns
$ python lands.py reigns --help

Usage: lands.py reigns [OPTIONS] COMMAND [ARGS]...

Options:
  --help  Show this message and exit.

Commands:
  conquer
  destroy

// And the help for towns
$ python lands.py towns --help

Usage: lands.py towns [OPTIONS] COMMAND [ARGS]...

Options:
  --help  Show this message and exit.

Commands:
  burn
  found

Now try it, manage the lands through the CLI:

// Try the reigns command
$ python lands.py reigns conquer Gondor

Conquering reign: Gondor

$ python lands.py reigns destroy Nilfgaard

Destroying reign: Nilfgaard

// Try the towns command
$ python lands.py towns found Springfield

Founding town: Springfield

$ python lands.py towns burn Atlantis

Burning town: Atlantis

Deeply nested subcommands

Now let's say that all these commands in the lands.py CLI program should be part of the previous CLI program we built in the first example.

We want our CLI program to have these commands/command groups:

  • users:
    • create
    • delete
  • items:
    • create
    • delete
    • sell
  • lands:
    • reigns:
      • conquer
      • destroy
    • towns:
      • found
      • burn

This already is a quite deeply nested "tree" of commands/command groups.

But to achieve that, we just have to add the lands Typer app to the same main.py file we already had:

import typer

import items
import lands
import users

app = typer.Typer()
app.add_typer(users.app, name="users")
app.add_typer(items.app, name="items")
app.add_typer(lands.app, name="lands")

if __name__ == "__main__":
    app()

And now we have everything in a single CLI program:

// Check the main help
$ python main.py --help

Usage: main.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:
  items
  lands
  users

// Try some users commands
$ python main.py users create Camila

Creating user: Camila

// Now try some items commands
$ python main.py items create Sword

Creating item: Sword

// And now some lands commands for reigns
$ python main.py lands reigns conquer Gondor

Conquering reign: Gondor

// And for towns
$ python main.py lands towns found Cartagena

Founding town: Cartagena

Review the files

Here are all the files if you want to review/copy them:

reigns.py:

import typer

app = typer.Typer()


@app.command()
def conquer(name: str):
    typer.echo(f"Conquering reign: {name}")


@app.command()
def destroy(name: str):
    typer.echo(f"Destroying reign: {name}")


if __name__ == "__main__":
    app()

towns.py:

import typer

app = typer.Typer()


@app.command()
def found(name: str):
    typer.echo(f"Founding town: {name}")


@app.command()
def burn(name: str):
    typer.echo(f"Burning town: {name}")


if __name__ == "__main__":
    app()

lands.py:

import typer

import reigns
import towns

app = typer.Typer()
app.add_typer(reigns.app, name="reigns")
app.add_typer(towns.app, name="towns")

if __name__ == "__main__":
    app()

users.py:

import typer

app = typer.Typer()


@app.command()
def create(user_name: str):
    typer.echo(f"Creating user: {user_name}")


@app.command()
def delete(user_name: str):
    typer.echo(f"Deleting user: {user_name}")


if __name__ == "__main__":
    app()

items.py:

import typer

app = typer.Typer()


@app.command()
def create(item: str):
    typer.echo(f"Creating item: {item}")


@app.command()
def delete(item: str):
    typer.echo(f"Deleting item: {item}")


@app.command()
def sell(item: str):
    typer.echo(f"Selling item: {item}")


if __name__ == "__main__":
    app()

main.py:

import typer

import items
import lands
import users

app = typer.Typer()
app.add_typer(users.app, name="users")
app.add_typer(items.app, name="items")
app.add_typer(lands.app, name="lands")

if __name__ == "__main__":
    app()

Tip

All these files have an if __name__ == "__main__" block just to demonstrate how each of them can also be an independent CLI app.

But for your final application, only main.py would need it.

Recap

That's it, you can just add Typer applications one inside another as much as you want and create complex CLI programs while writing simple code.

You can probably achieve a simpler CLI program design that's easier to use than the example here. But if your requirements are complex, Typer helps you build your CLI app easily.

Tip

Auto completion helps a lot, specially with complex programs.

Check the docs about adding auto completion to your CLI apps.