Why does my use of click.argument produce "got an unexpected keyword argument 'help'?

Question

Running the following code results in this error:

TypeError: init() got an unexpected keyword argument 'help'

Code:

import click  @click.command() @click.argument('command', required=1, help="start|stop|restart") @click.option('--debug/--no-debug', default=False, help="Run in foreground") def main(command, debug):     print (command)     print (debug)  if __name__ == '__main__':     main() 

Full error output:

$ python3 foo.py start Traceback (most recent call last):   File "foo.py", line 5, in <module>     @click.option('--debug/--no-debug', default=False, help="Run in foreground")   File "/home/cbetti/python/lib/python3/dist-packages/click-4.0-py3.4.egg/click/decorators.py", line 148, in decorator     _param_memo(f, ArgumentClass(param_decls, **attrs))   File "/home/cbetti/python/lib/python3/dist-packages/click-4.0-py3.4.egg/click/core.py", line 1618, in __init__     Parameter.__init__(self, param_decls, required=required, **attrs) TypeError: __init__() got an unexpected keyword argument 'help' 

Why does this error occur?

Answer 1

I run into this again and again because the trace output does not correspond to the parameter causing the error. Notice ArgumentClass in the trace, that's your hint.

'help' is an acceptable parameter to @click.option. The click library prefers, however, that you document your own arguments. The @click.argument help parameter is causing this exception.

This code works: (notice the lack of , help="start|stop|restart" in @click.argument)

import click  @click.command() @click.argument('command', required=1) @click.option('--debug/--no-debug', default=False, help="Run in foreground") def main(command, debug):     """ COMMAND: start|stop|restart """     print (command)     print (debug)  if __name__ == '__main__':         main() 

Output:

$ python3 foo.py start start False 

Help Output:

Usage: test.py [OPTIONS] COMMAND    COMMAND: start|stop|restart  Options:   --debug / --no-debug  Run in foreground   --help                Show this message and exit. 

Answer 2

You are defining commands as arguments. Note that click has a better way to define commands then what you are trying here.

@click.group() def main():     pass  @main.command() def start():     """documentation for the start command"""     print("running command `start`")  @main.command() def stop():     """documentation for the stop command"""     print("running command `stop`")  if __name__ == '__main__':     main() 

will result in the following default help text:

Usage: test_cli.py [OPTIONS] COMMAND [ARGS]...  Options:   --help  Show this message and exit.  Commands:   start  documentation for the start command   stop   documentation for the stop command 

Having said that, should you really need arguments, you cannot use the help parameter. The click documentation indeed states that you should document your own arguments. However, I have no idea how to do that. Any hints?

EDIT

As mentioned in the comments: this is to align with the Unix standard to document arguments in the main help text.