One of the more unique features of Python is the ability to collect all excess parameters passed to a method in a tuple (positional arguments) or a dictionary (keyword arguments).

This last method parameter often follows the “**kwargs” convention in the code I’ve run into.

When a final formal parameter of the form **name is present, it receives a dictionary containing all keyword arguments except for those corresponding to a formal parameter. This may be combined with a formal parameter of the form *name (described in the next subsection) which receives a tuple containing the positional arguments beyond the formal parameter list. (*name must occur before **name.) For example, if we define a function like this:

def cheeseshop(kind, *arguments, **keywords):
print "-- Do you have any", kind, '?'
print "-- I'm sorry, we're all out of", kind
for arg in arguments: print arg
print '-'*40
keys = keywords.keys()
keys.sort()
for kw in keys: print kw, ':', keywords[kw]

It could be called like this:

cheeseshop('Limburger', "It's very runny, sir.",
"It's really very, VERY runny, sir.",
client='John Cleese',
shopkeeper='Michael Palin',
sketch='Cheese Shop Sketch')

and of course it would print:

– Do you have any Limburger ?
– I’m sorry, we’re all out of Limburger
It’s very runny, sir.
It’s really very, VERY runny, sir.
—————————————-
client : John Cleese
shopkeeper : Michael Palin

sketch : Cheese Shop Sketch