Why is it that this one change in my code did not allow the while loop to go on forever?-CodePudding

i have an awfully simple and obtuse question, i hope this is the right place to ask this:

i wrote a program that generates two random integers, adds them together and prompts the user for an answer. if the user gets it wrong the question is prompted again until they get it right-- this is where the while loop comes into play and so i implemented it like this:

import random

number1 = random.randint(0, 99)
number2 = random.randint(0, 99)

answer = eval(input("What is {numberA}   {numberB}? ".format(numberA=number1, numberB=number2)))
check = answer == number1   number2
if answer == number1   number2:
    print("{numberA}   {numberB} = {Answer}".format(numberA=number1, numberB=number2, Answer=answer))
while answer != number1   number2:
    eval(input("That's not right. Try again: "))

print("yes that is right")

what ended up happening instead was that while loop ended up going on forever, when i instead changed the while statement to this:

while answer != number1   number2:
    answer = eval(input("That's not right. Try again: "))

it worked and the print statement that followed it was executed it immediately. what i don't understand was why did my mistake make the loop go on for infinity? how does redefining the answer variable in that statement make the while loop condition false?

CodePudding user response：

In your erroneous version, answer never changes, so once your code enters the loop (because answer != number1 number2) the condition remains true forever.

CodePudding user response：

You never modified answer in your original code. If the condition existed where the loop would start, nothing ever changed the state so that the test would fail and the loop would end.

CodePudding user response：

import random

number1 = random.randint(0, 99)
number2 = random.randint(0, 99)

correct_answer = number1   number2

answer = int(input("What is {numberA}   {numberB}? ".format(numberA=number1, numberB=number2)))

while answer != number1   number2:

    answer = int(input("That's not right. Try again: ".format(numberA=number1, numberB=number2)))
    
    if answer == correct_answer:
        break

print("yes that is right")

CodePudding user response：

answer never changes, you can fix this by simply adding

   if answer == correct_answer:
        break

in the

while answer != number1   number2:

loop.