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Python Exception Handling
- 3. Exception ï‚— An abnormal situation that is occurred in a program. RTS tech
- 4. Exception Hierarchy RTS tech BaseException Exception RuntimError ImportError ArithmeticError … ZeroDivisionError NoImplementationError ModuleNotFoundError … … …
- 5. Exception handling Exception Handling Exception Raised. RTS tech
- 6. Exception Handling ï‚— Exception causes abnormal termination of the program. ï‚— Python provides exception handling mechanism. ï‚— try-except-finally-else block is used to handle the exception in python. ï‚— Exception raised: ï‚— By system ï‚— By programmer using raise keyword RTS tech
- 7. Exceptional situation ï‚— a=2 ï‚— print("a=",a,"b=",b) ï‚— Output: ï‚— print("a=",a,"b=",b) ï‚— NameError: name 'b' is not defined RTS tech Exception Class Exception Message
- 8. Handle exception ï‚— a=2 ï‚— try: ï‚— print("a=",a,"b=",b) ï‚— except NameError: ï‚— print("check you variable Declration") ï‚— ï‚— Exception Handling RTS tech Exception Raised
- 9. How to Handle Exception ï‚— try-except-finally-else block is used to handle the exception. ï‚— try block raised an exception which is later handled by except block. ï‚— except block is used to provide alternative flow. ï‚— finally block is used to clean the resources like file, DB etc. ï‚— else block executed when there is no exception in the program. RTS tech
- 10. How to get exception Message  a=2  try:  print("a=",a,"b=",b)  except NameError as e:  print(“Error:",e) RTS tech
- 11. Handle Multiple exception ï‚— try: ï‚— a=int(input("Enter a Dividend n")) ï‚— b=int(input("Enter the divisorn")) ï‚— result=a/b ï‚— print("Division is {}".format(result)) ï‚— except ValueError: ï‚— print("Enter Integer Number") ï‚— except ZeroDivisionError: ï‚— print("Divisor can not 0") RTS tech
- 12. Parent Exception block ï‚— try: ï‚— a=int(input("Enter a Dividend n")) ï‚— b=int(input("Enter the divisorn")) ï‚— result=a/b ï‚— print("Division is {}".format(result)) ï‚— except Exception as e: ï‚— print("Error ",e) ï‚— We can use parent Exception class to handle the multiple exception in down hierarchy. RTS tech
- 13. try-except-else-finally ï‚— try: ï‚— a=int(input("Enter a Dividend n")) ï‚— b=int(input("Enter the divisorn")) ï‚— result=a/b ï‚— except ZeroDivisionError: ï‚— print("Divisor can not 0") ï‚— else: ï‚— print("Division is {}".format(result)) ï‚— finally: ï‚— print("I used for cleanup Task") ï‚— print("I always executed either exception is raised or not in try block") RTS tech
- 14. Built in Exception ï‚— AttributeError ï‚— Fail to reference an assignment to a variable. ï‚— EOFError ï‚— Reading beyond the file length ï‚— ImportError ï‚— not able to import function from module ï‚— ModuleNotFoundError ï‚— Module name is not available. ï‚— IndexError ï‚— Beyond the index we are trying to access the element from array, list, string etc. RTS tech
- 15. Built in exception(cont.) ï‚— keyError ï‚— Mapping key is not available. ï‚— NameError ï‚— Attribute is not defined. ï‚— NoImplementationError ï‚— When abstract method is not get implemented in child class ï‚— ValueError ï‚— When wrong type of value is going to be assigned ï‚— ZeroDivisionError ï‚— Trying to divide a number by zero RTS tech
- 16. User Define Exception ï‚— We can create user define exception using ï‚— raise keyword ï‚— Or by extending Exception base class to create our own exception Class. RTS tech
- 17. raise custom Exception ï‚— try: ï‚— age=int(input("Enter Your age: ")) ï‚— if(age<18): ï‚— raise Exception("You don't have rights to cast vote.") ï‚— else: ï‚— print("You have rights to cast vote") ï‚— except Exception as e: ï‚— print("Error ",e) RTS tech
- 18. Custom Exception Class ï‚— class InavalidVoterException(Exception): ï‚— def __init__(self): ï‚— super().__init__("Invalid Voter") ï‚— RTS tech
- 19. Test Custom Exception ï‚— from customException import InavalidVoterException ï‚— try: ï‚— age=int(input("Enter Your age: ")) ï‚— if(age<18): ï‚— raise InavalidVoterException() ï‚— else: ï‚— print("You have rights to cast vote") ï‚— except InavalidVoterException as e: ï‚— print("Error ",e) RTS tech
- 20. Disclaimer ï‚— This is a educational Presentation to make programming easier. ï‚— We have used images of different URLs to make presentation better. ï‚— We respect the work of the owners of the URLs. RTS tech
- 21. Thank You! RTS Tech. :rtstech30@gmail.com :+91 8818887087