Option groups¶
The @option_group decorator¶
The recommended way of defining option groups is through the
option_group()
decorator. This decorator is overloaded with two
signatures that only differ by how you provide the optional help
argument:
# help as keyword argument
@option_group(title, *options, help=None, ...)
# help as 2nd positional argument
@option_group(title, help, *options, ...)
Here’s the full list of parameters:
title – title of the help section describing the option group
*options – an arbitrary number of decorators like those returned by
cloup.option
andclick.option
. Since v0.9, each decorator can add even multiple options in a row. This was introduced to support constraints as decoratorshelp – an optional description shown below the title; can be provided as keyword argument or 2nd positional argument
constraint – an optional instance of Constraint (see Constraints for more info); a description of the constraint will be shown between squared brackets aside the option group title (or below it if too long)
hidden – if True, the option group and all its options are hidden from the help page (all contained options will have their hidden attribute set to True).
import cloup
from cloup import option_group, option
from cloup.constraints import RequireAtLeast
@cloup.command()
@option_group(
"Input options",
option("--one", help="1st input option"),
option("--two", help="2nd input option"),
option("--three", help="3rd input option"),
)
@option_group(
"Output options",
"This is a an optional description of the option group.",
option("--four / --no-four", help="1st output option"),
option("--five", help="2nd output option"),
option("--six", help="3rd output option"),
constraint=RequireAtLeast(1),
)
# The following will be shown (with --help) under "Other options"
@option("--seven", help="1st uncategorized option")
@option("--height", help="2nd uncategorized option")
def cli(**kwargs):
"""A CLI that does nothing."""
print(kwargs)
cli()
Usage: clouptest [OPTIONS]
A CLI that does nothing.
Input options:
--one TEXT 1st input option
--two TEXT 2nd input option
--three TEXT 3rd input option
Output options: [at least 1 required]
This is a an optional description of the option group.
--four / --no-four 1st output option
--five TEXT 2nd output option
--six TEXT 3rd output option
Other options:
--seven TEXT 1st uncategorized option
--height TEXT 2nd uncategorized option
--help Show this message and exit.
Options that are not assigned to an option group are included is the so called
default option group, which is shown for last in the --help
.
This group is titled “Other options” unless it is the only option group, in
which case cloup.Command
behaves like a normal click.Command
,
naming it just “Options”.
In the example above, I used the cloup.option()
decorator to define options
but that’s not required: you can use click.option()
or any other decorator
that acts like it. Nonetheless:
Tip: prefer Cloup decorators over Click ones
Cloup provides detailed type hints for (almost) all arguments you can pass to parameter and command decorators. This translates to a better IDE support, i.e. better auto-completion and error detection.
Aligned vs non-aligned groups¶
By default, all option group help sections are aligned, meaning that they
share the same column widths. Many people find this visually pleasing and this
is also the default behavior of argparse
.
Nonetheless, if some of your option groups have shorter options, alignment may result in a lot of wasted space and definitions quite far from option names, which is bad for readability. See this biased example to compare the two modes:
Usage: clouptest [OPTIONS]
A CLI that does nothing.
Input options:
--one TEXT This description is more likely to be wrapped
when aligning.
--two TEXT This description is more likely to be wrapped
when aligning.
--three TEXT This description is more likely to be wrapped
when aligning.
Output options:
--four This description is more likely to be wrapped
when aligning.
--five TEXT This description is more likely to be wrapped
when aligning.
--six TEXT This description is more likely to be wrapped
when aligning.
Other options:
--seven [a|b|c|d|e|f|g|h|i] First uncategorized option.
--height TEXT Second uncategorized option.
--help Show this message and exit.
Usage: clouptest [OPTIONS]
A CLI that does nothing.
Input options:
--one TEXT This description is more likely to be wrapped when aligning.
--two TEXT This description is more likely to be wrapped when aligning.
--three TEXT This description is more likely to be wrapped when aligning.
Output options:
--four This description is more likely to be wrapped when aligning.
--five TEXT This description is more likely to be wrapped when aligning.
--six TEXT This description is more likely to be wrapped when aligning.
Other options:
--seven [a|b|c|d|e|f|g|h|i] First uncategorized option.
--height TEXT Second uncategorized option.
--help Show this message and exit.
In Cloup, you can format each option group independently from each other
setting the @command
parameter align_option_groups=False
.
Since v0.8.0, this parameter is also available as a Context
setting:
from cloup import Context, group
CONTEXT_SETTINGS = Context.settings(
align_option_groups=False,
...
)
@group(context_settings=CONTEXT_SETTINGS)
def main():
pass
Note
The problem of aligned groups can sometimes be solved decreasing the
HelpFormatter
parameter col1_max_width
, which defaults to 30.
Alternative APIs¶
Option groups without nesting¶
While I largely prefer @option_group
, you may not like the additional level
of indentation it requires. In that case, you may prefer the following way
of defining option groups:
from cloup import OptionGroup
from cloup.constraints import SetAtLeast
# OptionGroup takes all arguments of @option_group but *options
input_grp = OptionGroup(
'Input options', help='This is a very useful description of the group'
)
output_grp = OptionGroup('Output options', constraint=SetAtLeast(1))
@cloup.command()
@input_grp.option('--one')
@input_grp.option('--two')
@output_grp.option('--three')
@output_grp.option('--four')
def cli_flat(one, two, three, four):
"""A CLI that does nothing."""
print(kwargs)
The above notation is just syntax sugar on top of @cloup.option
:
@input_grp.option('--one')
# is equivalent to:
@cloup.option('--one', group=input_grp)
Option groups without decorators¶
For some reason, you may need to work at a lower level, by passing parameters
to a Command
constructor. In that case you can use cloup.Option
(or the alias GroupedOption
):
from cloup import Command, Option, OptionGroup
output_opts = OptionGroup("Output options")
params = [
Option('--verbose', is_flag=True, group=output_opts),
...
]
cmd = Command(..., params=params, ...)
Reusing/modularizing option groups¶
Some people have asked how to reuse option groups in multiple commands and how
to put particularly long option groups in their own files. This is easy if you
know how Python decorator works. First, you store the decorator returned by
option_group
(called without a @
) in a variable:
from cloup import option_group
output_options = option_group(
"Output options",
option(...),
option(...),
...
)
Then you can use the decorator as many times as you want:
@command()
# other decorators...
@output_options
# other decorators ...
def foo()
...
Of course, if output_options
is defined in a different file, don’t forget to
import it!
Terminology-nazi note
It’s worth noting that output_options
in the example above is not
an option group, it’s just a function that recreate the same OptionGroup
object and all its options every time it is called. So, technically, you’re
not “reusing an option group”.
How it works¶
This feature is implemented simply by annotating each option with an additional
attribute group
of type Optional[OptionGroup]
. Unless the option is of
class cloup.Option
, this group
attribute is added and set by monkey-patching.
When the Command
is instantiated, it groups all options by their group
attribute. Options that don’t have a group
attribute (or have it set to
None
) are stored in the “default option group” (together with --help
).
In order to show option groups in the command help, OptionGroupMixin
“overrides” Command.format_options
.
Feature support¶
This features depends on two mixins:
(required)
OptionGroupMixin
(optional)
ConstraintMixin
, if you want to use constraints.
New!
Since Cloup v0.14.0, cloup.Group
supports option groups and constraints too.