TYPES OF EXCEPTION IN PYTHON

Exceptions are categorized into two categories. They are –

1. Pre-defined Exceptions – The runtime errors representation class which are present in python software are known as pre-defined exceptions. Example – value error, zero division error, key error, index error, name error etc. Pre-defined exceptions raised automatically whenever corresponding runtime error is occurred. After raising the pre-defined exceptions programmers handle those exceptions by using try and except blocks.

2. User defined Exceptions – The runtime errors representation which are defined by the programmers explicitly according to their business requirements are known as user defined exceptions. Any user defined class which is extending any one of the pre-defined exceptions class is known as a user defined exception class.

Syntax –

class classname(predefined exception classname)

----------

----------

----------

User defined exceptions will not raise automatically so that we have to rise those exceptions explicitly.

Note – Creating the runtime error representation class object is known as raising the exception.

We can raise the exceptions explicitly by using raise keyword.

Syntax – raise userdefinedexception

Note – We can also raise the pre-defined exceptions explicitly by using raise keyword.

After raising the exception we can handle that exception using try and except blocks.

Example –

class Error(Exception) :

    """ Base class for other exceptions """

pass

class valueTooSmallError(Error):

    """ Raised when the input value is too large"""

pass

class valueTooLargeError(Error):

    """ Raised when the input value is too small"""

pass

num=10

while True:

    try :

        i_num=input('Enter a number : ')

        if i_num<num:

            raise valueTooSmallError

        elif i_num>num :

            raise valueTooLargeError

        break

    except valueTooSmallError:

        print 'This value is too small, please try again'

    except valueTooLargeError:

        print 'This value is too large, please try again'

print 'Congratulation, at
last you successfully succeeded'

Output –

Enter a number : 8

This value is too small, please try again

Enter a number : 12

This value is too large, please try again

Enter a number : 10

Congratulation, at last you successfully succeeded