Callback in Python

 

What are Callbacks in Python?

A callback is a function that is passed as an argument to another function and is called later inside that function to complete a specific task.

In simple terms:

A callback is a function you give to another function so that it can call it when needed.

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✅ Why Use Callbacks?

• To customize the behavior of a function

• To handle events (e.g., in GUIs or web frameworks)

• To process results (e.g., in asynchronous programming)

• To simplify code reuse and abstraction

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✅ Basic Example of a Callback Function

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

def process_user(callback):
    user_name = "Alice"
    callback(user_name)

process_user(greet)

Output:

Hello, Alice!

📝 Here:

• greet is a callback function.

• process_user accepts the callback and calls it with data.

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✅ Example: Using Callbacks to Customize Behavior

def square(x):
    return x * x

def cube(x):
    return x * x * x

def apply_function(func, value):
    result = func(value)
    print(f"Result: {result}")

apply_function(square, 3)  # Output: Result: 9
apply_function(cube, 3)    # Output: Result: 27

📝 square and cube are callback functions passed to apply_function.

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✅ Real-World Example: Sorting with a Callback (Key Function)

names = ["Charlie", "Alice", "Bob"]

# Sort based on the length of the name
sorted_names = sorted(names, key=lambda name: len(name))

print(sorted_names)  # Output: ['Bob', 'Alice', 'Charlie']

📝 The lambda here acts as a callback passed to sorted().

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✅ Summary

Term	Meaning
Callback	A function passed as an argument
Used in	Sorting, GUI events, web apps, async programming
Benefit	Flexible, reusable, customizable behavior