The Callback Function in Python

Lakshay Kapoor Oct 10, 2023
  1. Parallel Python
  2. Callback Function Definition in Python
The Callback Function in Python

In this article, you’ll have a deeper understanding of the Python callback function. Check out our sample program below, which demonstrates the function’s purpose.

Parallel Python

Parallel Python is a module offered by Python that helps in providing a proper mechanism for the parallel execution of a program in Python. These Python codes are generally on SMP or Systems with Multiple Processors and Clusters, which are computers that are connected through a network.

This module is both open-source and cross-platform, which is written only in Python. It is a very light module and is also very easy to install with any Python software.

Callback Function Definition in Python

In the Parallel Python Module, the submit function is known as the callback function. The callback function acts as an argument for any other function. The other function in which the callback function is an argument calls the callback function in its function definition. Other modules can call the callback function depending upon their requirements and their nature.

These callback functions generally come into play when asynchronous functions are used in the program. An asynchronous function is a function that sometimes works out of sync or asynchronously through tasks like a loop.

The program below will demonstrate the use of a callback function:

def Func_CallBack(c):
    print("File Length : ", c)

def File_Len(filepath, callback):
    i = open(filepath, "r")
    file_length = len(

if __name__ == "__main__":
    File_Length("randomfile.txt", Func_CallBack)

In this example, we first define a function called Func_CallBack, which returns the total length of the whole text file. Initially, the Func_CallBack function takes the file path and the callback modules as arguments. Finally, the function reads the whole file and returns the length of the file. In the end, the Func_CallBack function calls to the callback modules, which initially functioned as arguments.

Lakshay Kapoor avatar Lakshay Kapoor avatar

Lakshay Kapoor is a final year B.Tech Computer Science student at Amity University Noida. He is familiar with programming languages and their real-world applications (Python/R/C++). Deeply interested in the area of Data Sciences and Machine Learning.


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