6.21.3.5 Option attributes

6.21.3.5 Option attributes

The following option attributes may be passed as keyword arguments to parser.add_option(). If you pass an option attribute that is not relevant to a particular option, or fail to pass a required option attribute, optparse raises OptionError.

• action (default: "store")

  Determines optparse's behaviour when this option is seen on the command line; the available options are documented above.

• type (default: "string")

  The argument type expected by this option (e.g., "string" or "int"); the available option types are documented below.

• dest (default: derived from option strings)

  If the option's action implies writing or modifying a value somewhere, this tells optparse where to write it: dest names an attribute of the options object that optparse builds as it parses the command line.

• default (deprecated)

  The value to use for this option's destination if the option is not seen on the command line. Deprecated; use parser.set_defaults() instead.

• nargs (default: 1)

  How many arguments of type type should be consumed when this option is seen. If > 1, optparse will store a tuple of values to dest.

• const

  For actions that store a constant value, the constant value to store.

• choices

  For options of type "choice", the list of strings the user may choose from.

• callback

  For options with action "callback", the callable to call when this option is seen. See section 6.21.4, Option Callbacks for detail on the arguments passed to callable.

• callback_args, callback_kwargs

  Additional positional and keyword arguments to pass to callback after the four standard callback arguments.

• help

  Help text to print for this option when listing all available options after the user supplies a help option (such as "-help"). If no help text is supplied, the option will be listed without help text. To hide this option, use the special value SUPPRESS_HELP.

• metavar (default: derived from option strings)

  Stand-in for the option argument(s) to use when printing help text. See section 6.21.2, the tutorial for an example.

---

Python Library Reference

Previous: 6.21.3.4 Standard option actions Up: 6.21.3 Reference Guide Next: 6.21.3.6 Standard option types

---

Release 2.4.4c1, documentation updated on 11 October 2006.