6.20.4.2 How callbacks are called
All callbacks are called as follows:
func(option, opt, value, parser, *args, **kwargs)
where
- option
- is the Option instance that's calling the callback.
- opt
- is the option string seen on the command-line that's triggering the callback. (If an
abbreviated long option was used, opt will be the full, canonical option
string--for example, if the user puts --foo on the command-line
as an abbreviation for --foobar, then opt will be --foobar.)
- value
- is the argument to this option seen on the command-line. optparse
will only expect an argument if type is set; the type of value will
be the type implied by the option's type (see 6.20.3, ``Option types''). If type
for this option is
None (no argument expected), then value will be
None. If "nargs > 1", value
will be a tuple of values of the appropriate type.
- parser
- is the OptionParser instance driving the whole thing, mainly
useful because you can access some other interesting data through it, as instance
attributes:
- parser.rargs
- the current remaining argument list, i.e. with opt (and value,
if any) removed, and only the arguments following them still there. Feel free to
modify parser.rargs, e.g. by consuming more arguments.
- parser.largs
- the current set of leftover arguments, i.e. arguments that have been processed but
have not been consumed as options (or arguments to options). Feel free to modify parser.largs e.g. by adding more arguments to it.
- parser.values
- the object where option values are by default stored. This is useful because it lets
callbacks use the same mechanism as the rest of optparse for
storing option values; you don't need to mess around with globals or closures. You can
also access the value(s) of any options already encountered on the command-line.
- args
- is a tuple of arbitrary positional arguments supplied via the callback_args
option attribute.
- kwargs
- is a dictionary of arbitrary keyword arguments supplied via callback_kwargs.
Since args and kwargs are optional (they are only passed if you
supply callback_args and/or callback_kwargs when you define your
callback option), the minimal callback function is:
def my_callback (option, opt, value, parser):
pass
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