Tutorial¶
A Simple Example¶
Let’s start with a simple example. Just use optgroup
for declaring option groups
by decorating your command function in Click-like API style.
# app.py
import click
from click_option_group import optgroup, RequiredMutuallyExclusiveOptionGroup
@click.command()
@optgroup.group('Server configuration',
help='The configuration of some server connection')
@optgroup.option('-h', '--host', default='localhost', help='Server host name')
@optgroup.option('-p', '--port', type=int, default=8888, help='Server port')
@optgroup.option('-n', '--attempts', type=int, default=3, help='The number of connection attempts')
@optgroup.option('-t', '--timeout', type=int, default=30, help='The server response timeout')
@optgroup.group('Input data sources', cls=RequiredMutuallyExclusiveOptionGroup,
help='The sources of the input data')
@optgroup.option('--tsv-file', type=click.File(), help='CSV/TSV input data file')
@optgroup.option('--json-file', type=click.File(), help='JSON input data file')
@click.option('--debug/--no-debug', default=False, help='Debug flag')
def cli(**params):
print(params)
if __name__ == '__main__':
cli()
Now we can see help for our app:
$ python app.py --help
Usage: app.py [OPTIONS]
Options:
Server configuration: The configuration of some server connection
-h, --host TEXT Server host name
-p, --port INTEGER Server port
-n, --attempts INTEGER The number of connection attempts
-t, --timeout INTEGER The server response timeout
Input data sources: [mutually_exclusive, required]
The sources of the input data
--tsv-file FILENAME CSV/TSV input data file
--json-file FILENAME JSON input data file
--debug / --no-debug Debug flag
--help Show this message and exit.
How It Works¶
Firstly, we declare the group using optgroup.group()
decorator:
@optgroup.group('Server configuration', help='The configuration of some server connection')
Note
Also we can declare groups just using optgroup()
:
@optgroup('Server configuration', help='The configuration of some server connection')
Secondly, we declare the grouped options below using optgroup.option()
decorator:
@optgroup.option('-h', '--host', default='localhost', help='Server host name')
@optgroup.option('-p', '--port', type=int, default=8888, help='Server port')
And that is all!
Checking Declarations¶
Attention
The important point: do not mix optgroup.option()
and click.option()
decorators!
click-option-group checks the decorators order and raises
the exception if optgroup.option()
and click.option()
decorators are mixed.
The following code is incorrect:
@optgroup.group('My group')
@click.option('--hello') # ERROR
@optgroup.option('--foo')
@click.option('--spam') # ERROR
@optgroup.option('--bar')
The correct code looks like:
@click.option('--hello')
@optgroup.group('My group')
@optgroup.option('--foo')
@optgroup.option('--bar')
@click.option('--spam')
If we try to use optgroup.option
without optgroup.grpup()
/optgroup()
declaration it also will raise the exception.
The following code is incorrect:
@click.command()
@click.option('--hello')
@optgroup.option('--foo') # ERROR: Missing declaration of the option group
@optgroup.option('--bar') # ERROR: Missing declaration of the option group
@click.option('--spam')
def cli(**params):
pass
If we declare only option group without the options it will raise warning.
@click.command()
@click.option('--hello')
@optgroup.group('My group') # WARN: The empty option group
@click.option('--spam')
def cli(**params):
pass
API Features¶
Besides optgroup
based decorators the package offers another way
to declare grouped options using OptionGroup
based class objects directly.
We can use the instances of these classes and use its OptionGroup.option()
method as
decorator for declaring and adding options to the group.
Here is an example how it looks:
import click
from click_option_group import OptionGroup, RequiredMutuallyExclusiveOptionGroup
server_config = OptionGroup('Server configuration', help='The configuration of some server connection')
input_sources = RequiredMutuallyExclusiveOptionGroup('Input data sources', help='The sources of the input data')
@click.command()
@server_config.option('-h', '--host', default='localhost', help='Server host name')
@server_config.option('-p', '--port', type=int, default=8888, help='Server port')
@input_sources.option('--tsv-file', type=click.File(), help='CSV/TSV input data file')
@input_sources.option('--json-file', type=click.File(), help='JSON input data file')
@click.option('--debug/--no-debug', default=False, help='Debug flag')
def cli(**params):
print(params)
if __name__ == '__main__':
cli()
In this case initially we create group objects and then we use OptionGroup.option()
method for
declaring options.
As well as in above example we cannot mix option
and click.option
decorators.
The following code is incorrect and will raise the exception:
@server_config.option('-h', '--host', default='localhost', help='Server host name')
@click.option('--foo') # ERROR
@server_config.option('-p', '--port', type=int, default=8888, help='Server port')
@input_sources.option('--tsv-file', type=click.File(), help='CSV/TSV input data file')
@click.option('--bar') # ERROR
@input_sources.option('--json-file', type=click.File(), help='JSON input data file')
Behavior and Relationship among Options¶
The groups are useful to define the specific behavior and relationship among grouped options.
click-option-groups provides two main classes: OptionGroup
and GroupedOption
.
OptionGroup
class is a new entity for Click that provides the abstraction for grouping options and manage it.GroupedOption
class is inherited fromclick.Option
and provides the functionality for grouped options.
OptionGroup
and GroupedOption
classes contain the basic functionality for support option groups.
Both these classes do not contain the specific behavior or relationship among grouped options.
The specific behavior can be implemented by using the inheritance, mainly, in OptionGroup
sub classes.
click-option-groups provides some useful OptionGroup
based classes out of the box:
RequiredAnyOptionGroup
– At least one option from the group must be setAllOptionGroup
– All options from the group must be set or none must be setRequiredAllOptionGroup
– All options from the group must be setMutuallyExclusiveOptionGroup
– Only one or none option from the group must be setRequiredMutuallyExclusiveOptionGroup
– Only one required option from the group must be set
OptionGroup
based class can be specified via cls
argument in optgroup()
/optgroup.group()
decorator or can be used directly when the second API way is used.
If you want to implement some complex behavior you can create a sub class of GroupedOption class and use
your GroupedOption
based class via cls
argument in optgroup.option
/OptionGroup.option
decorator method:
@click.command()
@optgroup('My group', cls=MyCustomOptionGroup)
@optgroup.option('--foo', cls=MyCustomGroupedOption)
...
Limitations¶
The package does not support nested option groups (option subgroups). This is intentional. Nested option groups complicate the implementation, API and CLI and most often it is not necessary.
If you think you need to nested option groups try redesign your CLI and doing it with nesting commands.