29 exception in python

 

1. An exception is an event, which occurs during the execution of a program.

2. Using try,except,else and finally block we can handle exception.

3. Using exceptions we can handle run time errors.

# else

1. else block will execute when the try block executed successfully with out any errors.

# Finally ***

1. finally block will execute both times when try block executed successfully or fail.

2. It is used to do the cleanup process.

1) try and except 

import sys

d = {'A':1,'B':2}

try:

    d['C']

    'we' + '123'

    sys.ok()

    import re

    open('2_else.py')

except ModuleNotFoundError:

    print(' Module is not defined ')

except NameError:

    print(' name is not defined please define ')

except KeyError:

    print(' KeyError ')

except FileNotFoundError as e:

    print(' Please define file ', e)

except:

    print(' Try block got failed ')

2)else block

#'''

#1. else block will execute when the try block executed successfully with out any errors.

#'''

try:

    a = '10'

    b = '20'

    c = a + b

except:

    print(' Try block got failed ')

else:

    print('Else block is')

3) finally

#'''

#1. finally block will execute both times when try block executed successfully or fail.

#2. It is used to do cleanup process

(Closing File, Killing process, close remote connections like that).

#'''

try:

    fh = open('3_finally.py')

    print(fh.readline())

    print('12' + '13')

except:

    print(' Try block got failed')

else:

    print(' Else block ')

finally:

    fh.close()

    print(' Finally block ')

4) raise exception

# Using raise keyword we can raise exception manually.

num = 13

if num <= 15 :

    raise AssertionError(' Number should be more than 15')

print(' END ')