Python，而While循环无法正常运行

Question

The while loop correctly stops when "no" is entered first for the "would you like to continue" question. When "no" is entered after "yes" or after several "yes" entries, then the user must answer "no" for however many "yes" entries came before it: eg "yes", "yes", "no" will produce two "would you like to continue" questions after the first "no" answer.

I am just beginning to learn Python, so any suggestions would be helpful.

Thank you.

def testing3():
    def Grade(score):
        if score >= 90:
            letter = "A"
        elif score >= 80:
            letter = "B"
        elif score >= 70:
            letter = "C"
        elif score >= 60:
            letter = "D"
        else:
            letter = "F"
        print(letter) 

    def main():
        x = input("Enter Numerical Grade: ")
        numGrade = int(x)
        Grade(numGrade)

    main()

    def main2():
        while True:
            test = input("Would you like to continue?: ")
            if test == 'Yes':
                testing3()
            else:
                print("Done")
                break

    main2()

testing3()

Answer 1

Your testing3 call invokes the inner main2 def, but main2 invokes the testing3 def so you are ping-ponging between the two.

To get a sense of this you should look at your stack-frames and you should see a frame for testing3 followed by testing2 followed by testing3 etc for how ever many times you have entered yes.

Whether or not you meant to (I don't think you did) you created a recursive function. So the reason you are having to enter no multiple times is as you unwind up (popping frames off the stack)

Answer 2

The proper use of the while loop should something like:

finish = False
while not finish:
  # do your stuff here
  finish = evaluateLoopFinish()

Here, finish is a signal flag which you must evaluate at the end of each turn. The first time is set at False, so not False == True, hence enters the loop.

Another tip: use only one main like this

def main(args):
  # do your stuff here

if __name__=="__main__":
  main()

Every Python script has a name special variable which holds the name of the module except for the script which was given to Python to be executed which receives the special value main .