# How to pass optional parameters to a function in Python?

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A type of argument with a default value is a Python optional parameter. A function definition's assignment operator or the Python **kwargs statement can be used to assign an optional argument. Positional and optional arguments are the two sorts of arguments that a Python function can take. Values that are not required to be given in order to call a function are known as optional parameters.

## Function in Python

A function is a section of code that only executes when called. You can supply parameters that is data to a function. As a result, a function may or may not return data.

### Example

Let us understand what a function in python is with the help of an example.

def demo_function():
print("Hello World")
demo_function() #the demo_function() method is called.


### Output

The output obtained is as follows.

Hello World


## Arguments in a Function

Functions accept arguments that can contain data. The function name is followed by parenthesis that list the arguments. Simply separate each argument with a comma to add as many as you like. The function in the following example only takes one argument (fname). A first name is passed to the function when it is called, and it is utilized there to print the whole name.

## Optional Arguments in Python

An argument in Python that has a default value is called an optional argument. A default value for an argument can be specified using the assignment operator. When calling a function, there is no requirement to provide a value for an optional argument. This is because, in the absence of a value, the default value will be used.

Argument default values are possible. This renders an argument unnecessary. If a default value is present for an argument, it will be used if no alternative value is provided.

Python has two primary methods for passing optional parameters. They are as follows.

• Without utilizing keyword justifications.

• Use keyword justifications.

## Passing without using keyword arguments

The following are some major considerations when passing without keyword arguments −

• When invoking a function, the order of the parameters—that is, the order in which the parameters are defined in the function—should be preserved.

• The non-optional arguments' values must be provided otherwise an error will be thrown.

• The default argument value can either be supplied or disregarded.

### Example

Let’s look at an example to see how optional arguments are passed.

# Python program to demonstrate a optional argument.
def function(a, b=999):
return a+b
print(function(2, 3))
# In the function 1 is represented as 'a' in the function and
#The function uses the default value of b
print(function(1))


### Output

The following is the output that is generated upon executing the above program.

5
1000

Updated on 16-Sep-2022 07:40:14