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User Defined Exception in Python 

Theory

In Python, an exception is an error that occurs during program execution and interrupts the normal flow of the program.

Sometimes the built-in exceptions are not enough for a program. In such cases, programmers can create their own exceptions called User Defined Exceptions.

A user defined exception is created by defining a new class that inherits from the Exception class.

This helps programmers handle custom errors based on specific conditions in the program.

Syntax

class ExceptionName(Exception):
    pass

Basic Example Program

# User Defined Exception Example

class AgeError(Exception):
    pass

age = int(input("Enter your age: "))

try:
    if age < 18:
        raise AgeError
    else:
        print("You are eligible to vote")

except AgeError:
    print("Error: Age must be 18 or above")

Sample Output

Case 1

Enter your age: 20
You are eligible to vote

Case 2

Enter your age: 15
Error: Age must be 18 or above

Explanation

  • class AgeError(Exception) → Creates a user defined exception

  • raise AgeError → Raises the custom exception

  • try block → Contains risky code

  • except block → Handles the error

✅ Conclusion:
User defined exceptions allow programmers to create custom error handling mechanisms, making programs more controlled and reliable.

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