twisted.python.usage.Options(dict) class documentation

An option list parser class

optFlags and optParameters are lists of available parameters which your program can handle. The difference between the two is the 'flags' have an on(1) or off(0) state (off by default) whereas 'parameters' have an assigned value, with an optional default. (Compare '--verbose' and '--verbosity=2')

optFlags is assigned a list of lists. Each list represents a flag parameter, as so:

  optFlags = [['verbose', 'v', 'Makes it tell you what it doing.'],
              ['quiet', 'q', 'Be vewy vewy quiet.']]

As you can see, the first item is the long option name (prefixed with '--' on the command line), followed by the short option name (prefixed with '-'), and the description. The description is used for the built-in handling of the --help switch, which prints a usage summary.

optParameters is much the same, except the list also contains a default value:

  optParameters = [['outfile', 'O', 'outfile.log', 'Description...']]

A coerce function can also be specified as the last element: it will be called with the argument and should return the value that will be stored for the option. This function can have a coerceDoc attribute which will be appended to the documentation of the option.

subCommands is a list of 4-tuples of (command name, command shortcut, parser class, documentation). If the first non-option argument found is one of the given command names, an instance of the given parser class is instantiated and given the remainder of the arguments to parse and self.opts[command] is set to the command name. For example:

  subCommands = [
       ['inquisition', 'inquest', InquisitionOptions,
            'Perform an inquisition'],
       ['holyquest', 'quest', HolyQuestOptions,
            'Embark upon a holy quest']
   ]

In this case, "<program> holyquest --horseback --for-grail" will cause HolyQuestOptions to be instantiated and asked to parse ['--horseback', '--for-grail']. Currently, only the first sub-command is parsed, and all options following it are passed to its parser. If a subcommand is found, the subCommand attribute is set to its name and the subOptions attribute is set to the Option instance that parses the remaining options. If a subcommand is not given to parseOptions, the subCommand attribute will be None. You can also mark one of the subCommands to be the default:

  defaultSubCommand = 'holyquest'

In this case, the subCommand attribute will never be None, and the subOptions attribute will always be set.

If you want to handle your own options, define a method named opt_paramname that takes (self, option) as arguments. option will be whatever immediately follows the parameter on the command line. Options fully supports the mapping interface, so you can do things like 'self["option"] = val' in these methods.

Shell tab-completion is supported by this class, for zsh only at present. Zsh ships with a stub file ("completion function") which, for Twisted commands, performs tab-completion on-the-fly using the support provided by this class. The stub file lives in our tree at twisted/python/twisted-completion.zsh, and in the Zsh tree at Completion/Unix/Command/_twisted.

Tab-completion is based upon the contents of the optFlags and optParameters lists. And, optionally, additional metadata may be provided by assigning a special attribute, compData, which should be an instance of Completions. See that class for details of what can and should be included - and see the howto for additional help using these features - including how third-parties may take advantage of tab-completion for their own commands.

Advanced functionality is covered in the howto documentation, available at http://twistedmatrix.com/projects/core/documentation/howto/options.html, or doc/core/howto/options.xhtml in your Twisted directory.