Option groups¶
The @option_group decorator¶
The recommended way of defining option groups is through the decorator
option_group()
.
-
cloup.
option_group
(name, *args, **kwargs)[source] Returns a decorator that annotates a function with an option group.
The
help
is an optional description and can be provided either as keyword argument or as 2nd positional argument after thename
of the group:# help as keyword argument @option_group(name, *options, help=None, ...) # help as 2nd positional argument @option_group(name, help, *options, ...)
- Parameters
name – this is shown as heading of the help section describing the option group.
help – an optional description shown below the name; can be provided as keyword argument or 2nd positional argument.
options – an arbitrary number of decorators like click.option, which annotate the input function with one
Option
.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 theirhidden
attribute set toTrue
).
import cloup
from cloup import option_group, option
from cloup.constraints import SetAtLeast
@cloup.command('clouptest')
@option_group(
"Input options",
"This is a very long description of the option group. I don't think this is "
"needed very often; still, if you want to provide it, you can pass it as 2nd "
"positional argument or as keyword argument 'help' after all options.",
option('-o', '--one', help='1st input option'),
option('--two', help='2nd input option'),
option('--three', help='3rd input option'),
)
@option_group(
'Output options',
option('--four / --no-four', help='1st output option'),
option('--five', help='2nd output option'),
option('--six', help='3rd output option'),
constraint=RequireAtLeast(1),
)
# Options that don't belong to any option group (including --help)
# are shown under "Other options"
@option('--seven', help='first uncategorized option',
type=click.Choice(['yes', 'no', 'ask']))
@option('--height', help='second uncategorized option')
def cli(**kwargs):
""" A CLI that does nothing. """
print(kwargs)
Usage: clouptest [OPTIONS]
A CLI that does nothing.
Input options:
This is a very long description of the option group. I don't think this is
needed very often; still, if you want to provide it, you can pass it as
2nd positional argument or as keyword argument 'help' after all options.
-o, --one TEXT 1st input option
--two TEXT 2nd input option
--three TEXT 3rd input option
Output options: [at least 1 required]
--four / --no-four 1st output option
--five TEXT 2nd output option
--six TEXT 3rd output option
Other options:
--seven [yes|no|ask] first uncategorized option
--height TEXT second uncategorized option
--help Show this message and exit.
The default option group
Options that are not assigned to any user-defined option group are listed
under a section which is shows at the bottom. This section is titled
“Other options”, unless the default group is the only one defined, 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 you can use click.option()
as well. There’s no practical difference
between the two when using @option_group
.
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 max_col1_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('clouptest')
# Input options
@input_grp.option('-o', '--one', help='1st input option')
@input_grp.option('--two', help='2nd input option')
# Output options
@output_grp.option('--four / --no-four', help='1st output option')
@output_grp.option('--five', help='2nd output option')
def cli_flat(**kwargs):
""" A CLI that does nothing. """
print(kwargs)
Equivalently, you could pass the option group as an argument to cloup.option
:
@cloup.option('-o', '--one', help='1st input option', group=input_grp)
Note that, in both cases, OptionGroup
instances work as “markers” for
options, not as containers of options: when you add an option nothing happens
to the corresponding option group.
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 GroupedOption
:
from cloup import Command, GroupedOption, OptionGroup
output_opts = OptionGroup("Output options")
params = [
GroupedOption('--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 GroupedOption
, this group
attribute is added and set by monkey-patching.
When the command is initialized, OptionGroupMixin
groups all options by
their group
attribute. Options that don’t have a group
attribute or have
it set to None
are put into 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.
cloup.Command
is the only command class that supports this feature, including
both these mixins.
Attention
cloup.Group
doesn’t support option groups nor constraints.
This is intentional: a Group
should have only a few options, so they
should not need neither option groups nor constraints. (But I may be wrong;
if you disagree, open an issue describing your use case). Anyway, you can
easily subclass cloup.Group
to include the above mixins:
from cloup import ConstraintMixin, OptionGroupMixin, Group
class MyGroup(ConstraintMixin, OptionGroupMixin, Group):
pass