Page - 95 - in Programming for Computations – Python - A Gentle Introduction to Numerical Simulations with Python 3.6, Volume Second Edition

4.2 ProgrammingasaStep-WiseStrategy 95 score = score + points(a, b, user_answer) print(’Your score is now: {:d}’.format(score)) print(’\nFinished! \nYour final score: {:d} (max: {:d})’\ .format(score, N*N)) Running this code, the order of the questions will be generated anew with each execution(becauseoftherandomization),but thedialoguemay,forexample,appear like: *** Welcome to the times tables test! *** (To stop: ctrl-c) 5 * 5 = 25 Correct! Your score is now: 1 5 * 3 = 15 Correct! Your score is now: 2 9 * 9 = 81 Correct! Your score is now: 3 ... ... <longer printout... author’s comment> ... Finished! Your final score: 95 (max: 100) Great!Ourcodeseems to runsmoothly, sowhat canpossiblygowrongnow? Thiswill gowrong: *** Welcome to the times tables test! *** (To stop: ctrl-c) 3 * 2 = six Traceback (most recent call last): ... ... < longer printout... author’s comment > ... ValueError: invalid literal for int() with base 10: ’six’ If a user gives some unexpected input that the code is not prepared to handle, things can go very wrong! In this case, we get an error message (referring to some ValueError),sinceourprogramdoesnotunderstandthat“six”actuallymeans the number6. It would not be very professional to leave our program with this potential problem,soitshouldbefixed,buthow?Thegoodnewsisthatmodernprogramming languages,Pythoninclusive,dohavetherighttools todealwithsuchcases.Fornow, we will leave our code as it is, but we hereby add yet another step to our program developmentplan, and will solve the problem when we turn to exception handling inSect.5.2.Thatwill alsobringus to the fourthversionofourprogram,whichalso