User-defined Exceptions in Python

trishareddy11 — Thu, 06 May 2021 14:40:33 +0000

In Python user-defined exceptions ,users can define custom exceptions by creating a new class. This exception class has to be derived, either directly or indirectly, from the built-in Exception class.

CREATING A USER-DEFINED EXCEPTION CLASS

Here we created a new exception class i.e. User_Error. Exceptions need to be derived from the built-in Exception class, either directly or indirectly. Let’s look at the given example which contains a constructor and display method within the given class.

#class MyError is extented from super class Exception class User_Error(Exception): # constructor method def __init__(self,value): self.value = value # __str__display function def __str__(self): return(repr(self.value)) try: raise(User_Error("User defined error")) # Value of Exception is stored in error except User_Error as error: print('A New Exception occured:',error.value)

CREATING A USER-DEFINED EXCEPTION CLASS (USING MULTIPLE INHERITENCE)

Derived class Exceptions are created when a single module handles multiple several distinct errors. Here we created a base class for exceptions defined by that module. This base class is inherited by various user-defined class to handle different types of errors.

# define python user-defined exceptions class Error(Exception): """Base clase for other exceptions""" pass class Dividebyzero(Error): """Raised when the input value is zero""" pass try: i_num = int(input("Enter a number: ")) if i_num ==0: raise Dividebyzero except Dividebyzero: print("Input value is zero, try again!") print()

Creating a User-defined Exception class (standard Exceptions)

Runtime error is a built-in class which is raised whenever a generated error does not fall into mentioned categories. The program below explains how to use runtime error as base class and user-defined error as derived class.

# User defined error class Usererror(RuntimeError): def __init__(self,arg): self.args = arg try: raise Usererror("usererror") except Usererror as e: print (e.args)

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User-defined Exceptions in Python

CREATING A USER-DEFINED EXCEPTION CLASS

CREATING A USER-DEFINED EXCEPTION CLASS (USING MULTIPLE INHERITENCE)

Creating a User-defined Exception class (standard Exceptions)