Call a click command from code

Question

I have a function which is wrapped as a command using click. So it looks like this:

@click.command() @click.option('-w', '--width', type=int, help="Some helping message", default=0) [... some other options ...] def app(width, [... some other option arguments...]):     [... function code...] 

I have different use cases for this function. Sometimes, calling it through the command line is fine, but sometime I would also like to call directly the function

from file_name import app width = 45 app(45, [... other arguments ...])  

How can we do that? How can we call a function that has been wrapped as a command using click? I found this related post, but it is not clear to me how to adapt it to my case (i.e., build a Context class from scratch and use it outside of a click command function).

EDIT: I should have mentioned: I cannot (easily) modify the package that contains the function to call. So the solution I am looking for is how to deal with it from the caller side.

Answer 1

You can call a click command function from regular code by reconstructing the command line from parameters. Using your example it could look somthing like this:

call_click_command(app, width, [... other arguments ...]) 

Code:

def call_click_command(cmd, *args, **kwargs):     """ Wrapper to call a click command      :param cmd: click cli command function to call      :param args: arguments to pass to the function      :param kwargs: keywrod arguments to pass to the function      :return: None      """      # Get positional arguments from args     arg_values = {c.name: a for a, c in zip(args, cmd.params)}     args_needed = {c.name: c for c in cmd.params                    if c.name not in arg_values}      # build and check opts list from kwargs     opts = {a.name: a for a in cmd.params if isinstance(a, click.Option)}     for name in kwargs:         if name in opts:             arg_values[name] = kwargs[name]         else:             if name in args_needed:                 arg_values[name] = kwargs[name]                 del args_needed[name]             else:                 raise click.BadParameter(                     "Unknown keyword argument '{}'".format(name))       # check positional arguments list     for arg in (a for a in cmd.params if isinstance(a, click.Argument)):         if arg.name not in arg_values:             raise click.BadParameter("Missing required positional"                                      "parameter '{}'".format(arg.name))      # build parameter lists     opts_list = sum(         [[o.opts[0], str(arg_values[n])] for n, o in opts.items()], [])     args_list = [str(v) for n, v in arg_values.items() if n not in opts]      # call the command     cmd(opts_list + args_list) 

How does this work?

This works because click is a well designed OO framework. The @click.Command object can be introspected to determine what parameters it is expecting. Then a command line can be constructed that will look like the command line that click is expecting.

Test Code:

import click  @click.command() @click.option('-w', '--width', type=int, default=0) @click.option('--option2') @click.argument('argument') def app(width, option2, argument):     click.echo("params: {} {} {}".format(width, option2, argument))     assert width == 3     assert option2 == '4'     assert argument == 'arg'   width = 3 option2 = 4 argument = 'arg'  if __name__ == "__main__":     commands = (         (width, option2, argument, {}),         (width, option2, dict(argument=argument)),         (width, dict(option2=option2, argument=argument)),         (dict(width=width, option2=option2, argument=argument),),     )      import sys, time      time.sleep(1)     print('Click Version: {}'.format(click.__version__))     print('Python Version: {}'.format(sys.version))     for cmd in commands:         try:             time.sleep(0.1)             print('-----------')             print('> {}'.format(cmd))             time.sleep(0.1)             call_click_command(app, *cmd[:-1], **cmd[-1])          except BaseException as exc:             if str(exc) != '0' and \                     not isinstance(exc, (click.ClickException, SystemExit)):                 raise 

Test Results:

Click Version: 6.7 Python Version: 3.6.3 (v3.6.3:2c5fed8, Oct  3 2017, 18:11:49) [MSC v.1900 64 bit (AMD64)] ----------- > (3, 4, 'arg', {}) params: 3 4 arg ----------- > (3, 4, {'argument': 'arg'}) params: 3 4 arg ----------- > (3, {'option2': 4, 'argument': 'arg'}) params: 3 4 arg ----------- > ({'width': 3, 'option2': 4, 'argument': 'arg'},) params: 3 4 arg