Use args and kwargs in Python

In this article we will discuss about *args and **kwargs properties and their usage in Python.

To pass unspecified number of arguments to a function usually *args and **kwargs properties are used. The *args property is used to send a non-keyword variable length argument to a function call whereas **kwargs keyword is used to pass a keyword length of arguments to a function.

• Keyword arguments (or arguments) are the values that is preceded by an identifier "=" in a function call for e.g. "name=".

• The primary benefits of using *args and **kwargs are readability and convenience, but they should be used with care.

Note ? It is not necessarily required to write *args and **kwargs. There is only a need for the asterisk (*). For instance, you could write *var and **vars as well.

Usage of*args in Python

To pass a variable number of non-keyword arguments in the function, we need to utilize an asterisk (*) before the parameter name

Example

Following is an example to pass arguments in a function using *args -

def multiply (*args):
   print(args, type(args))
multiply(6,78)

Output

So, we can be confident that the method that receives these provided parameters creates a tuple with the same name as the parameter excluding *.

(6, 78) <class 'tuple'>

Example

Let's now multiply a variable number of arguments to our multiply() function as shown in the example below -

def multiply(*args):
   x = 1
   for i in args:
      x = x * i
   print ('The product of the numbers is:',x)
multiply(5,87)
multiply(8,11)
multiply(6,9,4,7)
multiply(2,11,98)

Output

Following is an output of the above code -

The product of the numbers is: 435
The product of the numbers is: 88
The product of the numbers is: 1512
The product of the numbers is: 2156

Note ? The name of the argument need not be args; it might be anything. It's numbers in this instance. The use of the name *args is, however, commonly accepted.

Usage of **kwargs in Python

We can provide a Python function with any number of keyword arguments by using **kwargs.

To indicate this kind of argument in the function, we use a double asterisk (**) before the parameter name shows that a dictionary of keyworded arguments with variablelength exists.

Example

Following is an example to pass arguments in a function using **kwargs -

def gadgets_price(**kwargs):
   print(kwargs,type(kwargs))
gadgets_price(laptop= 60000, smartphone=10000, earphones =500)

Output

The arguments are passed as a dictionary and create a dictionary inside the function with the same name as the parameter, except **, as can be seen.

{'laptop': 60000, 'smartphone': 10000, 'earphones': 500} <class 'dict'>

Example

Let's finish the gadgets_price () function now to return the total amount of all the gadgets as shown in the following example:

def gadgets_price(**items):
   total = 0
   for price in items.values():
      total += price
   return total
print('The net amount of the gadgets is:',(gadgets_price(laptop= 60000, smartphone=10000, earphones =500)))
print('The net amount of the gadgets is:',(gadgets_price(laptop= 60000, smartphone=10000, desktop =45768)))
print('The net amount of the gadgets is:',(gadgets_price(laptop= 60000, TV=85965)))

Output

Following is an output of the above code -

The net amount of the gadgets is: 70500
The net amount of the gadgets is: 115768
The net amount of the gadgets is: 145965

Note ? The name of the argument need not be kwargs; it might be anything. It is items in this instance. But using **kwargs as the name is typically accepted.

Using *args and **kwargs in function call

We can pass arguments into functions using *args and **kwargs.

Example

There are three parameters identified in the function as ?laptop', ?smartphone' and ?earphone'. Each of these arguments will be printed out by the function. Then, using the asterisk syntax, we may provide a variable into the function that is set to an iterable (in this case, a tuple) as shown in the example below -

def gadgets(laptop, smartphone, earphone):
   print('The first gadget is of:',laptop)
   print('The second gadget is of:',smartphone)
   print('The third gadget is of:',earphone)
args = ('Lenovo','Samsung','JBL')
gadgets(*args)

Output

Using the python gadgets.py command, we can run the program and get the output shown below -

The first gadget is of: Lenovo
The second gadget is of: Samsung
The third gadget is of: JBL

Note - The above program can also be changed to use an iterable list data type and an alternative variable name. Let's also combine the named parameter with the *args syntax:

def gadgets_price(laptop, smartphone, earphone):
   print('The first gadget is of price:',laptop)
   print('The second gadget is of price:',smartphone)
   print('The third gadget is of price:',earphone)
list = [15438,499]
gadgets_price(54000,*list)

The output of the above code is as follows -

The first gadget is of price: 54000
The second gadget is of price: 15438
The third gadget is of price: 499

Example

Similarly, you can call a function with the keyworded **kwargs parameters. We'll create a variable named kwargs, which will represent a dictionary with three key-value pairs, but you can call it anything you like, and provide it to a function with three arguments as shown below -

def gadgets_price(laptop, smartphone, earphone):
   print('The first gadget is of price:',laptop)
   print('The second gadget is of price:',smartphone)
   print('The third gadget is of price:',earphone)
kwargs = {'laptop':54678, 'smartphone':15893, 'earphone':499}
gadgets_price(**kwargs)

Output

Using the python some gadgets_price.py command, we can run the program and get the output shown below -

The first gadget is of price: 54678
The second gadget is of price: 15893
The third gadget is of price: 499