Exception handling in Python with try, except, and finally keywords.
The try, except, and finally are the keywords in Python for exception handling. An exception is a runtime error, that causes the program to stop.
Why we need exception handling? Exceptions are not the errors introduced intentionally, neither they are validation checks. An exception occurs if a program can not process the given data values.
For example, while writing a division function in a server program you forgot to put a validation of zero value for the divisor.
All works well until the divisor is non-zero. What if it is zero? If the program does not hadle this exception, the program will crash and the server needs to start again. Not a good practice at all.
With exception handling, server program will not stop and a user can print a message and read next request.
What try, except, and finally keywords do?
These are the keywords in python for exception handling. Each keyword has its own associated block of code. A try block contains the actual programmer’s code. The execution reaches the except where there is an exception in the try block and the code within finally block always executes.
try: #User application code except Exception: #Executes upon exception finally: #Always executes
Python code example – No exception – Division by zero
try: x = 6; print(x/2); except Exception: print("Exception while division"); finally: print("Execution Completed");
3.0 Execution Completed
Python code example – With exception
try: x = 6; print(x/0); except Exception: print("Exception while division"); finally: print("Execution Completed");
Exception while division Execution Completed
Print The exception – Know what exactly error where there could be multiple exceptions-
try: x = 6; print(x/0); except Exception as e: print('Exception :', e); finally: print("Execution Completed");
Exception : division by zero Execution Completed