Clever Geek Handbook

Smarter than if

I am trying to execute a command (of a kind) commands.

if 'Who' in line.split()[:3]:
    Who(line)   
elif 'Where' in line.split()[:3]:
    Where(line)
elif 'What' in line.split()[:3]:
    What(line)
elif 'When' in line.split()[:3]:
    When(line)
elif 'How' in line.split()[:3]:
    How(line)
elif "Make" in line.split()[:3]:
    Make(line)
elif "Can You" in line.split()[:3]:
    CY(line)
else:
    print("OK")

So, an explanation. If Who

, What

etc. They are located in the first three words of the command, then it performs the corresponding function. I just want to know if there is a smarter way to do this but many if

, elif

and else

?

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2 answers


Try to create a dictionary with the keys being the command names and the values ​​of the actual command functions. Example:



def who():
    ...

def where():
    ...

def default_command():
    ...

commands = {
    'who': who,
    'where': where,
    ...
}

# usage
cmd_name = line.split()[:3][0]  # or use all commands in the list
command_function = commands.get(cmd_name, default_command)
command_function()  # execute command
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Here's another approach, use the submit command from a library module cmd

:

import cmd

class CommandDispatch(cmd.Cmd):
    prompt = '> '

    def do_who(self, arguments):
        """
        This is the help text for who
        """
        print 'who is called with argument "{}"'.format(arguments)

    def do_quit(self, s):
        """ Quit the command loop """
        return True

if __name__ == '__main__':
    cmd = CommandDispatch()
    cmd.cmdloop('Type help for a list of valid commands')
    print('Bye')

The program above will start a command loop with a prompt '> '

. It provides 3 commands: help

(provided cmd.Cmd

), who

and quit

. Here's an example of interaction:



$ python command_dispatch.py 
Type help for a list of valid commands
> help

Documented commands (type help <topic>):
========================================
help  quit  who

> help who

        This is the help text for who

> who am I?
who is called with argument "am I?"
> who
who is called with argument ""
> quit
Bye

Notes:

  • docstring for your command will also act as help text.
  • cmd.Cmd

    takes care of all submission details so you can focus on implementing your command
  • If you want to provide a command with a name why

    , then create a method named do_why

    and this command will be available.
  • See the documentation for more information.
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