How to Pass a Function as an Argument in Python?

Today, I will discuss a very important topic related to functions in Python. In this tutorial, I will show you how to pass a function as an argument in Python with some real examples. This will help the Python function be more modular, reusable, and clean.

Why Pass a Function as an Argument in Python?

In Python, Passing a function as an argument allows you to create higher-order functions. These functions operate on other functions, either by taking them as arguments or returning them. This can be incredibly useful for scenarios like callbacks, event handling, or simply making your code more dynamic and flexible.

Syntax

In Python, functions are first-class citizens. This means you can pass them around as arguments to other functions, just like any other object (e.g., strings, integers, lists). Here’s a basic example to understand this:

def greet(name):
    return f"Hello, {name}!"

def execute_function(func, value):
    return func(value)

print(execute_function(greet, "Alice"))

In this example, greet is passed as an argument to execute_function. The execute_function then calls greet with the provided value.

Here is the output in the screenshot below:

Check out How to Call a Function in Python?

Pass a Function as an Argument in Python Examples

Now, let me show you some examples and scenarios where you need to pass a function as an argument in Python.

1. Using Functions as Callbacks

One common use case for passing functions as arguments in Python is in callback functions. Callbacks are often used for event handling or asynchronous programming.

Here is an example.

def on_success(result):
    print(f"Success: {result}")

def on_failure(error):
    print(f"Error: {error}")

def process_data(data, success_callback, failure_callback):
    try:
        # Simulate processing data
        result = data / 2
        success_callback(result)
    except Exception as e:
        failure_callback(e)

process_data(10, on_success, on_failure)

Here, on_success and on_failure are passed as callbacks to process_data. Depending on whether the data processing is successful or not, the respective callback is invoked.

Here is the output in the screenshot below:

2. Higher-Order Functions

In Python, higher-order functions either take other functions as parameters or return them as results. Let me show you an example.

def add(x, y):
    return x + y

def subtract(x, y):
    return x - y

def apply_operation(operation, a, b):
    return operation(a, b)

print(apply_operation(add, 5, 3))  # Output: 8
print(apply_operation(subtract, 5, 3))  # Output: 2

In this scenario, apply_operation is a higher-order function that takes another function (add or subtract) as an argument and applies it to the given numbers.

Check out Python Function Examples with Parameters

3. Using *args and **kwargs

You can also pass functions as an argument using *args and **kwargs for more dynamic and flexible function calls in Python.

Here is an example and the complete code.

def multiply(x, y):
    return x * y

def apply_operations(func, *args):
    return func(*args)

print(apply_operations(multiply, 4, 5))  # Output: 20

This method allows you to pass a variable number of arguments to the function, making it highly versatile.

You can see the exact output in the screenshot below:

4. Functional Programming with map, filter, and reduce

Python’s built-in functions like map, filter, and reduce are excellent examples of higher-order functions. There, you can pass functions as arguments in Python.

def square(x):
    return x * x

numbers = [1, 2, 3, 4, 5]
squared_numbers = list(map(square, numbers))
print(squared_numbers)  # Output: [1, 4, 9, 16, 25]

In this example, map takes the square function and applies it to each item in the numbers list.

I executed the above Python code and you can see the output in the screenshot below:

Conclusion

There are various scenarios, like callbacks, higher-order functions, or functional programming, where we need to pass a function as an argument in Python; in this tutorial, I explained how to pass a function as an argument in Python with examples. Bookmark this page, it will be helpful to you.