How to pass through Python args and kwargs?

Question

While I have a general understanding (I think) of Python\'s *args and **kwargs, I\'m having trouble understanding how to pass them from one function through to another. Her

Answer 1

You pass them with syntax mirroring the argument syntax:

self.save_name_for(*args, **kwargs)

Note that you do not need to pass in self; save_name_for is already bound.

Answer 2

The * and ** operators are used in two different situations.

1. When used as part of a function definition,

   def save_name_for(self, *args, **kwargs):
   

   it is used to signify an arbitrary number of positional or keyword arguments, respectively. The point to remember is that inside the function args will be a tuple, and kwargs will be a dict.

2. When used as part of a function call,

   args = (1, 2)
   kwargs = {'last': 'Doe', 'first': 'John'}
   self.save_name_for(*args, **kwargs)
   

   the * and ** act as unpacking operators. args must be an iterable, and kwargs must be dict-like. The items in args will be unpacked and sent to the function as positional arguments, and the key/value pairs in kwargs will be sent to the function as keyword arguments. Thus,

   self.save_name_for(*args, **kwargs)
   

   is equivalent to

   self.save_name_for(1, 2, last='Doe', first='John')
   

See also the saltycrane blog for an explanation with examples.