Unix-like Command style parent

Evennia contribution, Vincent Le Geoff 2017

This module contains a command class that allows for unix-style command syntax in-game, using –options, positional arguments and stuff like -n 10 etc similarly to a unix command. It might not the best syntax for the average player but can be really useful for builders when they need to have a single command do many things with many options. It uses the ArgumentParser from Python’s standard library under the hood.

To use, inherit UnixCommand from this module from your own commands. You need to override two methods:

  • The init_parser method, which adds options to the parser. Note that you should normally

    not override the normal parse method when inheriting from UnixCommand.

  • The func method, called to execute the command once parsed (like any Command).

Here’s a short example:

class CmdPlant(UnixCommand):

    Plant a tree or plant.

    This command is used to plant something in the room you are in.

      plant orange -a 8
      plant strawberry --hidden
      plant potato --hidden --age 5


    key = "plant"

    def init_parser(self):
        "Add the arguments to the parser."
        # 'self.parser' inherits **argparse.ArgumentParser**
                help="the key of the plant to be planted here")
        self.parser.add_argument("-a", "--age", type=int,
                default=1, help="the age of the plant to be planted")
        self.parser.add_argument("--hidden", action="store_true",
                help="should the newly-planted plant be hidden to players?")

    def func(self):
        "func is called only if the parser succeeded."
        # 'self.opts' contains the parsed options
        key = self.opts.key
        age = self.opts.age
        hidden = self.opts.hidden
        self.msg("Going to plant '{}', age={}, hidden={}.".format(
                key, age, hidden))

To see the full power of argparse and the types of supported options, visit [the documentation of argparse](https://docs.python.org/2/library/argparse.html).

exception evennia.contrib.unixcommand.ParseError[source]

Bases: Exception

An error occurred during parsing.

class evennia.contrib.unixcommand.UnixCommandParser(prog, description='', epilog='', command=None, **kwargs)[source]

Bases: argparse.ArgumentParser

A modifier command parser for unix commands.

This parser is used to replace argparse.ArgumentParser. It is aware of the command calling it, and can more easily report to the caller. Some features (like the “brutal exit” of the original parser) are disabled or replaced. This parser is used by UnixCommand and creating one directly isn’t recommended nor necessary. Even adding a sub-command will use this replaced parser automatically.

__init__(prog, description='', epilog='', command=None, **kwargs)[source]

Build a UnixCommandParser with a link to the command using it.

  • prog (str) – the program name (usually the command key).

  • description (str) – a very brief line to show in the usage text.

  • epilog (str) – the epilog to show below options.

  • command (Command) – the command calling the parser.

Keyword Arguments
  • keyword arguments are directly sent to (Additional) –

  • You will find them on the (argparse.ArgumentParser.) –

  • documentation](https ([parser's) – //docs.python.org/2/library/argparse.html).


It’s doubtful you would need to create this parser manually. The UnixCommand does that automatically. If you create sub-commands, this class will be used.


Return the usage line.


This method is present to return the raw-escaped usage line, in order to avoid unintentional color codes.


Return the parser help, including its epilog.


This method is present to return the raw-escaped help, in order to avoid unintentional color codes. Color codes in the epilog (the command docstring) are supported.


Print the usage to the caller.


file (file-object) – not used here, the caller is used.


This method will override argparse.ArgumentParser’s in order to not display the help on stdout or stderr, but to the command’s caller.


Print the help to the caller.


file (file-object) – not used here, the caller is used.


This method will override argparse.ArgumentParser’s in order to not display the help on stdout or stderr, but to the command’s caller.

class evennia.contrib.unixcommand.HelpAction(option_strings, dest, nargs=None, const=None, default=None, type=None, choices=None, required=False, help=None, metavar=None)[source]

Bases: argparse.Action

Override the -h/–help action in the default parser.

Using the default -h/–help will call the exit function in different ways, preventing the entire help message to be provided. Hence this override.

class evennia.contrib.unixcommand.UnixCommand(**kwargs)[source]

Bases: evennia.commands.command.Command

Unix-type commands, supporting short and long options.

This command syntax uses the Unix-style commands with short options (-X) and long options (–something). The argparse module is used to parse the command.

In order to use it, you should override two methods: - init_parser: this method is called when the command is created.

It can be used to set options in the parser. self.parser contains the argparse.ArgumentParser, so you can add arguments here.

  • func: this method is called to execute the command, but after the parser has checked the arguments given to it are valid. You can access the namespace of valid arguments in self.opts at this point.

The help of UnixCommands is derived from the docstring, in a slightly different way than usual: the first line of the docstring is used to represent the program description (the very short line at the top of the help message). The other lines below are used as the program’s “epilog”, displayed below the options. It means in your docstring, you don’t have to write the options. They will be automatically provided by the parser and displayed accordingly. The argparse module provides a default ‘-h’ or ‘–help’ option on the command. Typing |whelp commandname|n will display the same as |wcommandname -h|n, though this behavior can be changed.


The lockhandler works the same as for objects. optional kwargs will be set as properties on the Command at runtime, overloading evential same-named class properties.


Configure the argument parser, adding in options.


This method is to be overridden in order to add options to the argument parser. Use self.parser, which contains the argparse.ArgumentParser. You can, for instance, use its add_argument method.


Override to handle the command execution.

get_help(caller, cmdset)[source]

Return the help message for this command and this caller.

  • caller (Object or Player) – the caller asking for help on the command.

  • cmdset (CmdSet) – the command set (if you need additional commands).


docstring (str) – the help text to provide the caller for this command.


Process arguments provided in self.args.


You should not override this method. Consider overriding init_parser instead.

aliases = []
help_category = 'general'
key = 'command'
lock_storage = 'cmd:all();'