How To Use Optional Parameters Python

In this tutorial, we will explore how to use optional parameters in Python, which are an incredibly useful feature when writing functions. Optional parameters allow you to assign default values to function arguments, making them optional for the function caller. This can greatly simplify your code while providing flexibility and clean function signatures.

Step 1: Defining a function with optional parameters

To define a function with optional parameters, you need to assign default values to these parameters using the equal sign ‘=’ when declaring the function. Let’s take a look at an example function that calculates the power of a number:

In this function, we have two parameters: base and exponent. Here, exponent has a default value of 2, making it an optional parameter. If the caller does not provide the value for exponent, the function will use its default value.

Step 2: Calling a function with optional parameters

When calling a function with optional parameters, you can either pass the required arguments or use the default values.

Here are three different ways to call the power function from Step 1:

In the first call, we only provide the base argument, so the function uses the default value for exponent (2). In the second and third calls, we provide both base and exponent, either as positional or keyword arguments.

The output of these three calls can be found as follows:

Result 1: 9
Result 2: 9
Result 3: 27

Step 3: Using multiple optional parameters

You can have multiple optional parameters in a function. Let’s define a function with three parameters, where two of them are optional:

In this example, prefix and suffix both have default values, while name is a required argument. The function constructs a greeting message using the provided values or their defaults.

You can call this function in several ways:

Hello John!
Hi John!
Hello John?
Hi John?

You can mix positional and keyword arguments when calling the function, as demonstrated above.

Full code


In this tutorial, we have learned how to define and use optional parameters in Python functions.

Optional parameters help simplify your code and make it easier to use functions with default values. This feature can also improve the readability and flexibility of your functions.

Remember, optional parameters should be assigned default values and should be listed after the required parameters in the function definition.