Jacob Tomlinson
I love using typer for creating CLI tools in Python. It makes creating complex trees of subcommands really straightforward.
However, I often don’t want the command on its own to have functionality. Instead I just want it to print out the help text, like if I run git or docker on their own I expect them to print out their help text.
$ git
These are common Git commands used in various situations:
start a working area (see also: git help tutorial)
clone Clone a repository into a new directory
init Create an empty Git repository or reinitialize an existing one
...
This is not the default behaviour in typer so to set this we need to use the no_args_is_help flag.
app = typer.Typer(no_args_is_help=True)
Example
Here’s an example from the docs with two subcommands.
# main.py
import typer
app = typer.Typer()
@app.command()
def hello(name: str):
"Say hello"
print(f"Hello {name}")
@app.command()
def goodbye(name: str, formal: bool = False):
"Say goodbye"
if formal:
print(f"Goodbye Ms. {name}. Have a good day.")
else:
print(f"Bye {name}!")
if __name__ == "__main__":
app()
However, if I run main.py without specifying a subcommand I get an error message that isn’t very useful.
$ python main.py
Usage: main.py [OPTIONS] COMMAND [ARGS]...
Try 'main.py --help' for help.
Error: Missing command.
But if I set the no_args_is_help option when creating my app I get a more useful help.
# main.py
import typer
app = typer.Typer(no_args_is_help=True)
@app.command()
def hello(name: str):
"Say hello"
print(f"Hello {name}")
@app.command()
def goodbye(name: str, formal: bool = False):
"Say goodbye"
if formal:
print(f"Goodbye Ms. {name}. Have a good day.")
else:
print(f"Bye {name}!")
if __name__ == "__main__":
app()
$ python main.py
Usage: main.py [OPTIONS] COMMAND [ARGS]...
Options:
--install-completion [bash|zsh|fish|powershell|pwsh]
Install completion for the specified shell.
--show-completion [bash|zsh|fish|powershell|pwsh]
Show completion for the specified shell, to
copy it or customize the installation.
--help Show this message and exit.
Commands:
goodbye Say goodbye
hello Say hello
Now I can easily see that I can use the hello or goodbye subcommand.