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ErrorsCategories of ErrorsCompile-timeRuntimeLogical

ErrorsCompile-TimeWhat? These are syntactical errors found in the code, due to which programfails to compileExample Missing a colon in the statements llike if, while, for, def etcProgram Outputx = 1if x == 1print("Colon missing")py 1.0_compile_time_error.pyFile "1.0_compile_time_error.py", line 5if x == 1^SyntaxError: invalid syntaxx = 1#Indentation Errorif x == 1:print("Hai")print("Hello")py 1.1_compile_time_error.pyFile "1.1_compile_time_error.py", line 8print("Hello")^IndentationError: unexpected indent

ErrorsRuntime - 1What? When PVM cannot execute the byte code, it flags runtime errorExample Insufficient memory to store something or inability of the PVM toexecute some statement come under runtime errorsProgram Outputdef combine(a, b):print(a + b)#Call the combine functioncombine("Hai", 25)py 2.0_runtime_errors.pyTraceback (most recent call last):File "2.0_runtime_errors.py", line 7, in <module>combine("Hai", 25)File "2.0_runtime_errors.py", line 4, in combineprint(a + b)TypeError: can only concatenate str (not "int") to str"""Conclusion:1. Compiler will not check the datatypes.2.Type checking is done by PVM during run-time."""

ErrorsRuntime - 2What? When PVM cannot execute the byte code, it flags runtime errorExample Insufficient memory to store something or inability of the PVM toexecute some statement come under runtime errorsProgram Output#Accessing the item beyond the arrayboundslst = ["A", "B", "C"]print(lst[3])py 2.1_runtime_errors.pyTraceback (most recent call last):File "2.1_runtime_errors.py", line 5, in <module>print(lst[3])IndexError: list index out of range

ErrorsLogical-1What? These errors depicts flaws in the logic of the programExample Usage of wrong formulasProgram Outputdef increment(sal):sal = sal * 15 / 100return sal#Call the increment()sal = increment(5000.00)print("New Salary: %.2f" % sal)py 3.0_logical_errors.pyNew Salary: 750.00

ErrorsLogical-2What? These errors depicts flaws in the logic of the programExample Usage of wrong formulasProgram Output#1. Open the filef = open("myfile", "w")#Accept a, b, store the result of a/b into the filea, b = [int(x) for x in input("Enter two number: ").split()]c = a / b#Write the result into the filef.write("Writing %d into myfile" % c)#Close the filef.close()print("File closed")py 4_effect_of_exception.pyEnter two number: 10 0Traceback (most recent call last):File "4_effect_of_exception.py", line 8, in<module>c = a / bZeroDivisionError: division by zero

ErrorsCommonWhen there is an error in a program, due to its sudden termination, the following thingscan be suspectedThe important data in the files or databases used in the program may be lostThe software may be corruptedThe program abruptly terminates giving error message to the user making the userlosing trust in the software

ExceptionsIntroductionAn exception is a runtime error which can be handled by the programmerThe programmer can guess an error and he can do something to eliminate the harm caused bythat error called an ‘Exception’BaseExceptionExceptionStandardError WarningArthmeticErrorAssertionErrorSyntaxErrorTypeErrorEOFErrorRuntimeErrorImportErrorNameErrorDeprecationWarningRuntimeWarningImportantWarning

ExceptionsException HandlingThe purpose of handling errors is to make program robustStep-1 try:statements#To handle the ZeroDivisionError Exceptiontry:f = open("myfile", "w")a, b = [int(x) for x in input("Enter two numbers: ").split()]c = a / bf.write("Writing %d into myfile" % c)Step-2 except exeptionname:statementsexcept ZeroDivisionError:print("Divide by Zero Error")print("Don't enter zero as input")Step-3 finally:statementsfinally:f.close()print("Myfile closed")

ExceptionsProgram#To handle the ZeroDivisionError Exception#An Exception handling Exampletry:f = open("myfile", "w")a, b = [int(x) for x in input("Enter two numbers: ").split()]c = a / bf.write("Writing %d into myfile" % c)except ZeroDivisionError:print("Divide by Zero Error")print("Don't enter zero as input")finally:f.close()print("Myfile closed")Output:py 5_exception_handling.pyEnter two numbers: 10 0Divide by Zero ErrorDon't enter zero as inputMyfile closed

ExceptionsException Handling Syntaxtry:statementsexcept Exception1:handler1except Exception2:handler2else:statementsfinally:statements

ExceptionsException Handling: Noteworthy- A single try block can contain several except blocks.- Multiple except blocks can be used to handle multiple exceptions.- We cannot have except block without the try block.- We can write try block without any except block.- Else and finally are not compulsory.- When there is no exception, else block is executed after the try block.- Finally block is always executed.

ExceptionsTypes: Program-1#To handle the syntax error given by eval() function#Example for Synatx errortry:date = eval(input("Enter the date: "))except SyntaxError:print("Invalid Date")else:print("You entered: ", date)Output:Run-1:Enter the date: 5, 12, 2018You entered: (5, 12, 2018)Run-2:Enter the date: 5d, 12m, 2018yInvalid Date

ExceptionsTypes: Program-2#To handle the IOError by open() function#Example for IOErrortry:name = input("Enter the filename: ")f = open(name, "r")except IOError:print("File not found: ", name)else:n = len(f.readlines())print(name, "has", n, "Lines")f.close()If the entered file is not exists, it will raise an IOError

ExceptionsTypes: Program-3#Example for two exceptions#A function to find the total and average of list elementsdef avg(list):tot = 0for x in list:tot += xavg = tot / len(list)return tot.avg#Call avg() and pass the listtry:t, a = avg([1, 2, 3, 4, 5, 'a'])#t, a = avg([]) #Will give ZeroDivisionErrorprint("Total = {}, Average = {}". format(t, a))except TypeError:print("Type Error: Pls provide the numbers")except ZeroDivisionError:print("ZeroDivisionError, Pls do not give empty list")Output:Run-1:Type Error: Pls provide the numbersRun-2:ZeroDivisionError, Pls do not give empty list

ExceptionsExcept Block: Various formatsFormat-1 except Exceptionclass:Format-2 except Exceptionclass as obj:Format-3 except (Exceptionclass1, Exceptionclass2, ...):Format-4 except:

ExceptionsTypes: Program-3A#Example for two exceptions#A function to find the total and average of list elementsdef avg(list):tot = 0for x in list:tot += xavg = tot / len(list)return tot.avg#Call avg() and pass the listtry:t, a = avg([1, 2, 3, 4, 5, 'a'])#t, a = avg([]) #Will give ZeroDivisionErrorprint("Total = {}, Average = {}". format(t, a))except (TypeError, ZeroDivisionError):print("Type Error / ZeroDivisionError”)Output:Run-1:Type Error / ZeroDivisionErrorRun-2:Type Error / ZeroDivisionError

ExceptionsThe assert StatementIt is useful to ensure that a given condition is True, It is not True, it raisesAssertionError.Syntax:assert condition, message

ExceptionsThe assert Statement: ProgramsProgram - 1 Program - 2#Handling AssertionErrortry:x = int(input("Enter the number between 5 and 10: "))assert x >= 5 and x <= 10print("The number entered: ", x)except AssertionError:print("The condition is not fulfilled")#Handling AssertionErrortry:x = int(input("Enter the number between 5 and 10: "))assert x >= 5 and x <= 10, "Your input is INVALID"print("The number entered: ", x)except AssertionError as Obj:print(Obj)

ExceptionsUser-Defined ExceptionsStep-1 class MyException(Exception):def __init__(self, arg):self.msg = argStep-2 raise MyException("Message")Step-3 try:#codeexcept MyException as me:print(me)

ExceptionsUser-Defined Exceptions: Program#To create our own exceptions and raise it when neededclass MyException(Exception):def __init__(self, arg):self.msg = argdef check(dict):for k, v in dict.items():print("Name = {:15s} Balance = {:10.2f}" . format(k, v)) if (v < 2000.00):raise MyException("Less Bal Amount" + k)bank = {"Raj": 5000.00, "Vani": 8900.50, "Ajay": 1990.00}try:check(bank)except MyException as me:print(me)

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