finally keyword in python

finally block is always executed in python irrespective of exception is raised or not within the program. Exception handling in python can be referred under chapter Python Exception Handling

In finally block we can handle closing of any open connections, files after the exception has been raised in the program or any additional steps to be performed prior to exiting the program.

Copy the below code into file expfinally.py and execute it or copy the code from GitHub

'''

    Module demonstrates exception Handling 

    and finally keyword

'''

def ConvertToInteger(x):

    ''' ConvertToInteger function 

        Converts passed argument to Integer

        Args:

            Takes an argument and converts to Integer

        Return:

            Returns an integer number.

            In case of Exception error code -1 is returned

    '''

    try:

        num = int(x)

    except:

        errCode = -1

        return errCode

    finally:

        print("finally block executed always with or without exception")

    return num

    

def CountWordsInfile(file):

    ''' CountWordsInfile function 

        Counts the total number of words in file

        Args:

            Takes a single argument fileName 

        Return:

            Return the number of words in the file

    '''

    try:

        fp = open(file, mode='rt', encoding='utf-8')

        data = fp.read()

        words = data.split()

        fp.close()

        print ("words in text file: ",len(words))

        return len(words)

    except Exception as error:

        print("Exception Occured and Exception is:")

        print(error)

    finally:

        print("finally block executed always with or without exception")

For details on docstrings how to use help on module refer to chapter Docstrings and Comments in Python

We have used help on module to refer to the functions inside the module. Demonstrated finally keyword in case of exception and without exception.

expfinally.ConvertToInteger('a') error code of -1 is returned in case of exception and finally block is also executed.

expfinally.ConvertToInteger('29') a valid number is returned after conversion without exception and finally block is also executed.