DSC 20 Lecture 15

Source: https://docs.google.com/presentation/d/15saIVRjgeoZB_ymuNC2Sa9nT4LpYJFsP/edit#slide=id.p1

Advanced Argument Passing

Argument Passing: Keyworded Arguments

When defining a function, you can specify only what you need

Default Arguments

Default = at the end
Order matters
Having a positional argument after a keyword argument will result in errors.

Arbitrary number of arguments

• Sometimes, we do not know in advance the number of arguments that will be passed into a function.
• We use an asterisk (*) before the parameter name to denote this kind of argument.
• These arguments get wrapped up into a tuple before being passed into the function.

**kwargs

• **kwargs allows you to write functions with arbitrary number of arguments with names (or keywords) associated with it.
• The number of arguments is variable, because you don’t know ahead how many arguments will the function get.

Order Matters

If you choose to use and combine the special matching modes, Python has two
ordering rules:

• In the call, keyword arguments must appear after all non keyword arguments.
• In a function header, the *args must be after normal arguments and
  defaults, and **kwargs must be last.
  def func(normal arguments, *args, **kwargs)