python - What is the purpose and use of **kwargs?

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Answer 1

You can use **kwargs to let your functions take an arbitrary number of keyword arguments ("kwargs" means "keyword arguments"):

>>> def print_keyword_args(**kwargs):
...     # kwargs is a dict of the keyword args passed to the function
...     for key, value in kwargs.iteritems():
...         print "%s = %s" % (key, value)
... 
>>> print_keyword_args(first_name="John", last_name="Doe")
first_name = John
last_name = Doe

You can also use the **kwargs syntax when calling functions by constructing a dictionary of keyword arguments and passing it to your function:

>>> kwargs = {'first_name': 'Bobby', 'last_name': 'Smith'}
>>> print_keyword_args(**kwargs)
first_name = Bobby
last_name = Smith

The Python Tutorial contains a good explanation of how it works, along with some nice examples.

Python 3 update

For Python 3, instead of iteritems(), use items()