Finally block in Python programming language

In Python programming language, the try-except block is quite commonly used to handle exceptions and error handling in code. However, there are times when we need to execute a piece of code regardless of whether there is an exception or not. This is where the finally block comes into play. The finally block is executed after the try and except blocks but before the code continues to the next statement. In this tutorial, we will cover the basics of the finally block in Python and how to use it to handle exceptions, clean up resources, and other important use cases.

try..except..finally construct in Python

• We have already read how try...except construct is used to handle exceptions in Python.
• There is an optional  finally  clause of the try..except statement.
• The code in the finally block is always executed.
• The code in the  finally  block is executed, whether an exception occurs or not.
• If there is no exception, the code in the  finally  block is executed after all the statements of  try  block.
• If exception occurs, the code in the  finally  block is executed after the code of the  except  block.
• In the code sample below we see that the  finally  block is always executed.
• Code Sample : 

def my_function(x, y):
    try:
        print("Inside try block")
        z = (x * y) / (x + y)
        print("Value of z = ", z)
    except Exception as e:
        print("Inside except block : ", e)
    finally:
        print("Inside Finally block")



my_function(5, -5)
print()
my_function(4, 1)


# Output
# Inside try block
# Inside except block :  division by zero
# Inside Finally block

# Inside try block
# Value of z =  0.8
# Inside Finally block

using finally block without except block

• We can omit the  except  clause if we choose to write the  finally  clause in the  try..except..finally  statement.
• Even if we do not write the  except  clause, the code in the  finally  block will always be executed 
• If we do not write the  except  clause,  exceptions will not be handled gracefully.
• If we do not write the  except  clause and an exception occurs, 
  • the code in the  finally  block will be executed and 
  • then the code execution will halt abruptly.
• Code Sample : 

def my_function(x, y):
    try:
        print("Inside try block")
        z = (x * y) / (x + y)
        print("Value of z = ", z)
    finally:
        print("Inside Finally block")



my_function(5, -5)


# Output
# Inside try block
# Inside Finally block
# ZeroDivisionError: division by zero

Uses of finally block

• The  finally  block can be used for tasks like 
  • cleaning up resources like - end connection from database, close any open file etc.
  • printing a message to user before program ends, even if there is an exception.