Callbacks

• The concept is a widely used programming technique.
• It allows you to pass a function as an argument to another function.
• The passed function is then called at a later point in time (e.g., in response to a specific event or action).

Basic principles of a callback function

1. Definition, e.g. my_callback(message)
   • Callback functions are basically regular functions that perform a specific task. However, they are not called directly, but passed to another function.
2. Passing the callback function, e.g. to process_data(data, callback)
   • The function that receives the callback stores it and calls it again at a later time, often when a certain condition is met or an event occurs.
3. Calling the callback function callback(f"Processed item: {result}")
   • The callback function is called within the function that received it, e.g., to display a message or process data.

Example

def my_callback(message):
    print(f"Callback received message: {message}")
 
def process_data(data, callback):
    for item in data:
        # Process the item
        result = item * 2
        # Call the callback function and pass the result
        callback(f"Processed item: {result}")
 
if __name__ == "__main__":
    data = [1, 2, 3, 4, 5]
    process_data(data, my_callback)

The output should look like this:

Callback received message: Processed item: 2
Callback received message: Processed item: 4
Callback received message: Processed item: 6
Callback received message: Processed item: 8
Callback received message: Processed item: 10