Exception Handling in Python✌

 

Exceptions ---> in Python

Normally error is an event that occurs when our code fails to follow the rules of a certain coding language, there are two kinds of error in python. They are,

1. Syntax error
2. Runtime error

        Syntax Error:

            These errors occur due to use of wrong syntax. These are handled by the coder manually.

        Runtime error:

            

            These error occur at the time of execution of program and these are not error made purposely.These happen due to unavoidable conditions.These errors are corrected by use of exception handling methods of the language in which the code is written.In python Exception handling is done by Try-Except block.

        

        The main thing to be remembered is exception handling only supports runtime errors and does not support syntax errors

Base Exception is the root of python Exception handler.

1. Normal Execution of Try-Except block

Example:

print('the try except concept')
try:
  print(1/0)
except ZeroDivisionError:
  print('we cannot divide by zero')

>>the try except concept

we cannot divide by zero

Here we are trying to overcome the zero division error which arises when any values divided by zero.

If you don't know the type of error you can simply use except: without mentioning any errors.

try:
  a=[1,2,3]
  print(a[5])
except error:
  print("Exception handeled")
>> Exception handled without mentioning errors

2. Use of message in Try-Except block:

Example:

try:
  print(1/0)
except ZeroDivisionError as ms:
  print('error raised because:',ms)

>>error raised because: division by zero

3. Control flow Execution:

Example:

try:
  statement -1
  statement -2
except error:
  statement-3
statement-4

>>
Case 1: No exception raised and program ran normal.
1,2,4 and normal 
Case 2: The statement 1 raises exception and program runs normal.
3,4 and normal
Case 3: The statement 1 runs normally but statement 2 raises exception.
The except block has a error in the statement 3,so the program terminates
abnormally.
1 and abnormal
Case 4: The statement 1 raises exception. Statement 3 has some error, so the code
terminates abnormally
abnormal 

4. Multiple Exceptional Block:

Example:




try:
    client_obj.get_url(url)
except (URLError, ValueError, SocketTimeout):
    client_obj.remove_url(url)

5. Single exceptional block that capture multiple exceptions

Example:

a=1,b=0
try:
    print(a/b)
    print("This won't be printed")
    print('10+10')
except TypeError:
    print("You added values of incompatible types")
except ZeroDivisionError:
    print("You Divided by Zero")

>>You Divided by Zero

6. finally block:

The statements inside the finally will be executed irrespective of any exceptions ie., they will be executed no matter if exception raises or not.

Example:

try:
  print(10/0)
except:
  print(10/0)
finally:
  print('i am final')

>>i am final

7. else block:

The statement under the else code runs when there is no exceptions.

Example:

try:
  print('10/0')
except:
  print('i am except')
else:
  print('hello python')
finally:
  print('i am final')

>>10/0
hello python
i am final

8. Nested try except block:

Example:

try:
    print("outer try block")
    try:
        print("Inner try block")
    except ZeroDivisionError:
        print("Inner except block")
    finally:
        print("Inner finally block")
except:
    print("outer except block")
finally:
    print("outer finally block")

>>outer try block

Inner try block

Inner finally block

outer finally block