Source: Uncle Mac Programming

This issue should be an old fan's request - three minutes to speak clearly what is the callback function (Callback Function).

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Definition
A callback function is when a pointer (address) to a function is passed as an argument to another function, and that pointer is used to call the function it points to. A callback function is not called directly by the implementer of the function, but by another party when a specific event or condition occurs, in response to that event or condition.

"To put the above obscure concepts into one sentence, "

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A callback function is a function that is passed as an argument.

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Example
Write a function with a calculator function in three lines of code

def calculator(v1,v2,fn): result = fn(v1,v2) return result
But this calculator doesn't do anything, and 1+1 doesn't compute.

Then write an add function to find the sum of two numbers.

def calculator(v1,v2,fn): result = fn(v1,v2) return result def add(v1,v2): return v1 + v2 # Call calculator and calculate 1+1 print(calculator(1,1,add))
Output results.

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The add function in the above code is called the callback function of the calculator.

Isn't it still pretty simple?

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Then don't you still write the callback functions for subtraction, multiplication and division to increase the impression?

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The difference between callback functions and recursive functions
A callback function is a function in which the "callback function" is passed in as an argument and is called inside the function.

A recursive function, on the other hand, is a function within a function that calls itself.

The difference between callback functions and higher-order functions
Remember the higher-order functions that appeared a few issues ago? Isn't the callback function kinda like it?

Recall the definition of a higher-order function.

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Python's higher-order function is actually a function that accepts a function as an argument, or a function that returns a function as a result is a higher-order function (higher-order function).

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And the definition of a callback function

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A callback function is a function that is passed as an argument.

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Any sense of the subtlety of this?

def calculator(v1,v2,fn): result = fn(v1,v2) return result def add(v1,v2): return v1 + v2
In the above code, the

calculator is a higher-order function, and add is a callback function.

More details ~

Finally
Thank you for your continued interest, I wonder if today's article is helpful to you?