class documentation

Information about how to convert command line strings to Python objects.

Action objects are used by an ArgumentParser to represent the information needed to parse a single argument from one or more strings from the command line. The keyword arguments to the Action constructor are also all attributes of Action instances.

Keyword Arguments:

  • option_strings -- A list of command-line option strings which

    should be associated with this action.

  • dest -- The name of the attribute to hold the created object(s)

  • nargs -- The number of command-line arguments that should be

    consumed. By default, one argument will be consumed and a single value will be produced. Other values include:

    • N (an integer) consumes N arguments (and produces a list)
    • '?' consumes zero or one arguments
    • '*' consumes zero or more arguments (and produces a list)
    • '+' consumes one or more arguments (and produces a list)

    Note that the difference between the default and nargs=1 is that with the default, a single value will be produced, while with nargs=1, a list containing a single value will be produced.

  • const -- The value to be produced if the option is specified and the

    option uses an action that takes no values.

  • default -- The value to be produced if the option is not specified.

  • type -- A callable that accepts a single string argument, and

    returns the converted value. The standard Python types str, int, float, and complex are useful examples of such callables. If None, str is used.

  • choices -- A container of values that should be allowed. If not None,

    after a command-line argument has been converted to the appropriate type, an exception will be raised if it is not a member of this collection.

  • required -- True if the action must always be specified at the

    command line. This is only meaningful for optional command-line arguments.

  • help -- The help string describing the argument.

  • metavar -- The name to be used for the option's argument with the

    help string. If None, the 'dest' value will be used as the name.

Method __call__ Undocumented
Method __init__ Undocumented
Method format_usage Undocumented
Instance Variable choices Undocumented
Instance Variable const Undocumented
Instance Variable default Undocumented
Instance Variable dest Undocumented
Instance Variable help Undocumented
Instance Variable metavar Undocumented
Instance Variable nargs Undocumented
Instance Variable option_strings Undocumented
Instance Variable required Undocumented
Instance Variable type Undocumented
Method _get_kwargs Undocumented

Inherited from _AttributeHolder:

Method __repr__ Undocumented
Method _get_args Undocumented