Python - args and kwargs

Today I am going to explain args and kwargs in python

So far I have learned that:

						
							 *args = list of arguments -as positional arguments
							 **kwargs = dictionary - whose keys become separate keyword arguments and the values become values of these arguments.

The names *args and **kwargs are only by convention but there's no need not to use them. You would use *args when you're not sure how many arguments might be passed to your function, i.e. it allows you pass an arbitrary number of arguments to your function. For example:


						
						>>> def print_everything(*args):
									 for count, thing in enumerate(args):
						...         print '{0}. {1}'.format(count, thing)
						...
						>>> print_everything('apple', 'banana', 'cabbage')
						0. apple
						1. banana
						2. cabbage

Similarly, **kwargs allows you to handle named arguments that you have not defined in advance:


						>>> def table_things(**kwargs):
						...     for name, value in kwargs.items():
						...         print '{0} = {1}'.format(name, value)
						...
						>>> table_things(apple = 'fruit', cabbage = 'vegetable')
						cabbage = vegetable
						apple = fruit

You can use these along with named arguments too. The explicit arguments get values first and then everything else is passed to *args and *kwargs. The named arguments come first in the list. For example:


						
						def table_things(titlestring, **kwargs)

You can also use both in the same function definition but *args must occur before **kwargs. You can also use the * and ** syntax when calling a function. For example:


						>>> def print_three_things(a, b, c):
						...     print 'a = {0}, b = {1}, c = {2}'.format(a,b,c)
						...
						>>> mylist = ['aardvark', 'baboon', 'cat']
						>>> print_three_things(*mylist)
						a = aardvark, b = baboon, c = cat

As you can see in this case it takes the list (or tuple) of items and matches them to the arguments in the function. Of course, you could have a * both in the function definition and in the function call.

Written by Vivek Soundrapandi

Published Date: {{ article.pub_date }}

View all posts by: Vivek Soundrapandi

Python - args and kwargs

Written by Vivek Soundrapandi

Published Date: {{ article.pub_date }}

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