为什么我的代码（Python 加减法）不起作用？

Question

Here is what I need coded:

• Detect user input for the words: "add" and "sub" aka subtraction.
• If the wrong answer is given, it should re-ask the question.
• If the user chooses either, it should generate two numbers from 1-9, number 1 >= number 2, and the user should be asked the answer.
• If the answer is correct, it should move to the next round (our teacher said there must be 5 rounds, at each end of the round the code should ask the user to type "add" or "sub" again.
• If the user gives the wrong answer, it should re-ask the question.
• The code ends when all 5 rounds are done, or if the user types "end" at any time with a message saying "Goodbye".

My code is:

import random

i = 1
while i < 6:
    answer1 = input("Hello, please type \"add\" for adding, or \"sub\" for subtracting")

    first_number = random.randrange(1, 9)
    second_number = random.randrange(1, first_number)
    one = str(first_number)
    two = str(second_number)

    if answer1 == "add":
        the_answer = first_number + second_number
        the_answer_actual = str(the_answer)
        user_answer = int(input(one + " + " + two + " = "))
        if the_answer == user_answer:
            print("The answer is correct!")
            i += 1
        elif the_answer != user_answer:
            print("Wrong answer. The correct answer was " + the_answer_actual)
            i += 1
        else:
            continue

    elif answer1 == "sub":
        the_answer = first_number - second_number
        the_answer_actual = str(the_answer)
        user_answer = int(input(one + " - " + two + " = "))
        if the_answer == user_answer:
            print("The answer is correct!")
            i += 1
        elif the_answer != user_answer:
            print("Wrong answer. The correct answer was " + the_answer_actual)
            i += 1
        else:
            continue

    elif answer1 == "end" or i < 6:
        print("Goodbye.")
        break

    else:
        pass

======================================================================== Problem: This error code appears when the 5th round is over:

• Traceback (most recent call last): -File "C:\Users\kingh\PycharmProjects\pythonProject\main.py", line 8, in
  • second_number = random.randrange(1, first_number)
  • File "C:\Users\kingh\AppData\Local\Programs\Python\Python39\lib\random.py", line 316, in randrange
    • raise ValueError("empty range for randrange() (%d, %d, %d)" % (istart, istop, width)) ValueError: empty range for randrange() (1, 1, 0)

Answer 1

You just need to convert the answer to an integer before comparing it:

if answer2 == int(user_answer):

and then it works perfectly (naturally you must do it for subtraction as well)

EDIT: and you need to add a break after the correct answer

print("The answer is correct!")
break

Answer 2

You need to do this in both add and sub as it doesn't work in either:

if str(answer2) == useranswer:

or

useranswer = int(input("..."))

as else you will be comparing a string with an int which will never work. the first solution converts the number you calculated to a string, the second solution converts the input you get from the user to an int. Both work, but you cannot compare a String with an int.

If you want to do more comparisons with the userinput (like checking if the result was bigger/lower than what you entered) i would reccomend the first solution, as you will alwats have the userinput as an int until you compare it.

Answer 3

You might need to use if ans2 == user_answer: instead of if answer2 == user_answer: since it is a string comparison.

EDIT: You might also want to use i += 1 instead to make sure it stops after the specified number of iterations.