Default Argument Values

In Python, it’s possible to set default values for function parameters. This feature allows you to call a function without providing all arguments, where unspecified arguments are initialized with default values.

Syntax of Default Argument Values

A default argument value is defined within the function’s parameter list in the definition. The parameter is followed by an equal sign (=) and then the default value.

Here is the basic syntax:

1def function_name(argument1=default_value1, argument2=default_value2):
2    # function body

In the example above, default_value1 and default_value2 are the default values for argument1 and argument2 respectively.

Example of Default Argument Values

Let’s take a look at a simple example of a function with default argument values.

1def greet(name, greeting="Hello"):
2    print(f"{greeting}, {name}!")
5greet("Bob", "Good morning")

In the first function call, only the name is provided, so the greeting is “Hello” by default. In the second function call, both name and greeting are provided, so the default greeting is overridden. The output will be:

Hello, Alice!
Good morning, Bob!

Importance of Default Argument Values

Python’s default argument feature provides flexible ways to call a function. It allows you to create more adaptable functions and can also simplify your code, making it easier to read and maintain. In addition, default arguments can prevent runtime errors when a function is called with missing arguments.


Default argument values are evaluated at the point of function definition in the defining scope. Therefore, if you use a mutable data type (like a list or a dictionary) as a default value, mutations will affect all subsequent calls of the function. If you want a fresh copy of the default value for each call, initialize it in the function body instead.

In conclusion, using default argument values in Python functions can enhance code functionality and flexibility. It is a crucial skill in Python programming that beginners should grasp.