CLI Options with Help
You already saw how to add a help text for CLI arguments with the help parameter.
Let's now do the same for CLI options:
import typer
def main(
name: str,
lastname: str = typer.Option("", help="Last name of person to greet."),
formal: bool = typer.Option(False, help="Say hi formally."),
):
"""
Say hi to NAME, optionally with a --lastname.
If --formal is used, say hi very formally.
"""
if formal:
print(f"Good day Ms. {name} {lastname}.")
else:
print(f"Hello {name} {lastname}")
if __name__ == "__main__":
typer.run(main)
We are replacing the default values we had before with typer.Option().
As we no longer have a default value there, the first parameter to typer.Option() serves the same purpose of defining that default value.
So, if we had:
lastname: str = ""
now we write:
lastname: str = typer.Option("")
And both forms achieve the same: a CLI option with a default value of an empty string ("").
And then we can pass the help keyword parameter:
lastname: str = typer.Option("", help="this option does this and that")
to create the help for that CLI option.
Copy that example from above to a file main.py.
Test it:
$ python main.py --help
Usage: main.py [OPTIONS] NAME
Say hi to NAME, optionally with a --lastname.
If --formal is used, say hi very formally.
Arguments:
NAME [required]
Options:
--lastname TEXT Last name of person to greet. [default: ]
--formal / --no-formal Say hi formally. [default: False]
--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.
// Now you have a help text for the --lastname and --formal CLI options 🎉
CLI Options help panels¶
The same as with CLI arguments, you can put the help for some CLI options in different panels to be shown with the --help option.
If you have installed Rich as described in the docs for Printing and Colors, you can set the rich_help_panel parameter to the name of the panel you want for each CLI option:
import typer
def main(
name: str,
lastname: str = typer.Option("", help="Last name of person to greet."),
formal: bool = typer.Option(
False, help="Say hi formally.", rich_help_panel="Customization and Utils"
),
debug: bool = typer.Option(
False, help="Enable debugging.", rich_help_panel="Customization and Utils"
),
):
"""
Say hi to NAME, optionally with a --lastname.
If --formal is used, say hi very formally.
"""
if formal:
print(f"Good day Ms. {name} {lastname}.")
else:
print(f"Hello {name} {lastname}")
if __name__ == "__main__":
typer.run(main)
Now, when you check the --help option, you will see a default panel named "Options" for the CLI options that don't have a custom rich_help_panel.
And below you will see other panels for the CLI options that have a custom panel set in the rich_help_panel parameter:
$ python main.py --help
<b> </b><font color="#F4BF75"><b>Usage: </b></font><b>main.py [OPTIONS] NAME </b>
<b> </b>
Say hi to NAME, optionally with a <font color="#A1EFE4"><b>--lastname</b></font>.
If <font color="#6B9F98"><b>--formal</b></font><font color="#A5A5A1"> is used, say hi very formally. </font>
<font color="#A5A5A1">â•â”€ Arguments ───────────────────────────────────────────────────────╮</font>
<font color="#A5A5A1">│ </font><font color="#F92672">*</font> name <font color="#F4BF75"><b>TEXT</b></font> [default: None] <font color="#A6194C">[required]</font> │
<font color="#A5A5A1">╰───────────────────────────────────────────────────────────────────╯</font>
<font color="#A5A5A1">â•â”€ Options ─────────────────────────────────────────────────────────╮</font>
<font color="#A5A5A1">│ </font><font color="#A1EFE4"><b>--lastname</b></font> <font color="#F4BF75"><b>TEXT</b></font> Last name of person to greet. │
<font color="#A5A5A1">│ </font><font color="#A1EFE4"><b>--install-completion</b></font> <font color="#F4BF75"><b> </b></font> Install completion for the │
<font color="#A5A5A1">│ current shell. │</font>
<font color="#A5A5A1">│ </font><font color="#A1EFE4"><b>--show-completion</b></font> <font color="#F4BF75"><b> </b></font> Show completion for the current │
<font color="#A5A5A1">│ shell, to copy it or customize │</font>
<font color="#A5A5A1">│ the installation. │</font>
<font color="#A5A5A1">│ </font><font color="#A1EFE4"><b>--help</b></font> <font color="#F4BF75"><b> </b></font> Show this message and exit. │
<font color="#A5A5A1">╰───────────────────────────────────────────────────────────────────╯</font>
<font color="#A5A5A1">â•â”€ Customization and Utils ─────────────────────────────────────────╮</font>
<font color="#A5A5A1">│ </font><font color="#A1EFE4"><b>--formal</b></font> <font color="#AE81FF"><b>--no-formal</b></font> Say hi formally. │
<font color="#A5A5A1">│ [default: no-formal] │</font>
<font color="#A5A5A1">│ </font><font color="#A1EFE4"><b>--debug</b></font> <font color="#AE81FF"><b>--no-debug</b></font> Enable debugging. │
<font color="#A5A5A1">│ [default: no-debug] │</font>
<font color="#A5A5A1">╰───────────────────────────────────────────────────────────────────╯</font>
Here we have a custom CLI options panel named "Customization and Utils".
Help with style using Rich¶
In a future section you will see how to use custom markup in the help for CLI options when reading about Commands - Command Help.
If you are in a hurry you can jump there, but otherwise, it would be better to continue reading here and following the tutorial in order.
Hide default from help¶
You can tell Typer to not show the default value in the help text with show_default=False:
import typer
def main(fullname: str = typer.Option("Wade Wilson", show_default=False)):
print(f"Hello {fullname}")
if __name__ == "__main__":
typer.run(main)
And it will no longer show the default value in the help text:
$ python main.py
Hello Wade Wilson
// Show the help
$ python main.py --help
Usage: main.py [OPTIONS]
Options:
--fullname TEXT
--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.
// Notice there's no [default: Wade Wilson] 🔥
Technical Details
In Click applications the default values are hidden by default. 🙈
In Typer these default values are shown by default. 👀