Custom Exception Handling with Multiple Processes in Python (using multiprocessing)

What will you learn?

Delve into the realm of custom exception handling while working with multiple processes in Python using the powerful multiprocessing module. Learn to define and manage your own exceptional scenarios to streamline your program’s flow effectively.

Introduction to the Problem and Solution

In the world of Python programming, managing exceptions is crucial, especially when dealing with multiple processes. Custom exception handling empowers you to define unique error situations and handle them gracefully. By leveraging the multiprocessing module, which facilitates parallel process creation and management, you can enhance error management within your applications.

To tackle this challenge successfully, it’s essential to comprehend how custom exceptions operate in a multiprocessing environment. Through defining and raising custom exceptions within individual processes, you gain the ability to navigate errors efficiently and optimize your program’s execution path.


import multiprocessing

class CustomException(Exception):

def process_function():
        # Your code that may raise an exception goes here
        raise CustomException("An error occurred")
    except CustomException as e:
        print(f"Custom Exception Handled: {e}")

if __name__ == "__main__":
    # Create a Process
    process = multiprocessing.Process(target=process_function)

    # Start the Process

    # Join the Process

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# Copyright PHD


  • Importing multiprocessing: Importing the necessary module for working with multiple processes.
  • Defining a Custom Exception: Creation of a custom exception named CustomException by inheriting from the base Exception class.
  • Process Function: The core function housing our main logic where we simulate an error scenario by raising a CustomException.
  • Handling Custom Exception: Within the process function, catching our custom exception type and handling it appropriately.
  • Main Block: Creating a new process, initiating it, waiting for its completion via joining, and executing our defined function within that isolated process space.
    How do I define a custom exception in Python?

    To create a custom exception in Python, establish a new class that inherits from either Exception or any other built-in exception class available in Python.

    Can I have multiple except blocks for different exceptions?

    Yes, you can utilize multiple except blocks after a try block to handle distinct types of exceptions individually based on your needs.

    Is there any limit on how many processes I can create using multiprocessing?

    The number of processes creatable using multiprocessing varies by system but is generally constrained by factors like available memory and system resources.

    What happens if an unhandled exception occurs within a child process?

    If an unhandled exception arises within a child process spawned by multiprocessing, it won’t propagate back to the parent unless explicitly managed within that child process itself.

    Are global variables shared between processes created by multiprocessing?

    No, each process possesses its memory space; thus global variables aren’t shared between them by default. Specific mechanisms like shared memory objects provided by multiprocessing are required for such sharing.


    Mastering custom exception handling alongside parallel processing instances is pivotal for building resilient applications. By comprehending how these concepts harmonize seamlessly through modules like ‘multiprocessing’, you elevate both functionality and reliability of your programs significantly.

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