背景：
对于我的计算机科学课，我们被要求创建一个帮助小学生学习基本数学的程序
他们会选择他们想要学习的操作（加法，减法，乘法或除法），或选择随机选择其中一项操作随机。
选择一个操作后，系统会询问用户一个问题，然后输入答案，如果程序正确，则会询问另一个问题，最多总共4个问题，然后程序将返回菜单。
如果答案不正确，则会要求用户再次输入答案，最多三次，如果答案仍然不正确，将显示正确答案，然后会询问另一个问题（如果未满足4个问题配额） ）如果没有其他问题，请返回菜单。
问题：
我写了所有的东西，当我在IDLE中运行程序时，一切似乎都在工作，但是由于某种原因选择了一个操作后，程序被卡在一个无限循环中，并且在询问了4个问题之后不会返回菜单。
我首先使用for循环来满足4个问题配额，但是没有用，所以我尝试了一个while循环，它读取while x<4: etc etc，在while循环之前将x定义为x = 0，然后在结束时功能添加x=x+1。
再次阅读代码，看起来它应该适用于每个函数，但在运行之后我仍然陷入无限循环。
继承人代码：
def show_instructions():
"""
Displays a greeting to the user and provides instructions on how to use the
program. [PURPOSE]
"""
print " "
print "-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-"
print " Math Mania"
print " "
print "Welcome to Math Mania! This program is designed to help you learn basic"
print "math skills in addition, subtraction, multiplication, and division."
print "-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-_-"
print " "
print "To learn a skill, type the first letter of that skill."
print " "
print "a for addition"
print "s for subtraction"
print "m for multiplication"
print "d for division"
print "r for random"
print "q to quit"
print " "
def add():
"""
generates display two random numbers and sums them, then prompts the user
to input the correct sum, if the input is incorrect, it prompts the user
to try again.
[PURPOSE]
"""
x=0
while x<4:
num1 = random.randint(1,20)
num2 = random.randint(1,20)
print num1, "+", num2, '= ?'
answer = input ('Enter your answer: ')
count1=0
while answer != num1+num2 and count1<3:
count1=count1 +1
print 'Incorrect, please try again.'
print
print num1, '+', num2, '= ?'
answer = input ('Enter your answer: ')
if count1==3:
print "Sorry, that's incorrect."
print "The correct answer is ",num1+num2
else:
print "That's correct!"
print
x=x+1
def sub():
"""
generates and displays two random numbers and subtracts the smaller of the
two from the larger one. It then prompts the user to input the correct
answer, if the input is incorrect, it prompts the user to try again.
[PURPOSE]
"""
x=0
while x<4:
num1 = random.randint(1,20)
num2 = random.randint(1,20)
if num1>num2:
print num1, "-", num2, '= ?'
answer = input('Enter your answer: ')
count1=0
while answer != num1 - num2 and count1<3:
count1=count1+1
print 'Incorrect, please try again.'
print
print num1, "-", num2, '= ?'
answer = input ('Enter your answer: ')
if count1==3:
print "Sorry, that's incorrect."
print "The correct answer is ",num1-num2
else:
print "That's correct!"
print
x=x+1
else:
print num2, "-", num1, '= ?'
answer = input ('Enter your answer')
count1=0
while answer!= num2-num1 and count1<3:
count1=count1+1
print 'Incorrect, please try again.'
print
print num2, "-", num1, '= ?'
answer = input ('Enter your answer: ')
if count1==3:
print "Sorry, that's incorrect."
print "The correct answer is ",num2-num1
else:
print 'Thats correct!'
print
x=x+1
def mult():
"""
generates and displays two random numbers and finds the product of the two.
It then prompts the user to input the correct product of the two numbers, if
the input is incorrect, it prompts the user to try again.
[PURPOSE]
"""
x=0
while x<4:
num1 = random.randint(1,20)
num2 = random.randint(1,20)
print num1, "x", num2, '= ?'
answer = input ('Enter your answer: ')
count1=0
while answer != num1*num2 and count1<3:
count1=count1+1
print 'Incorrect, please try again.'
print
print num1, 'x', num2, '= ?'
answer = input ('Enter your answer: ')
if count1==3:
print "Sorry, that's incorrect."
print "The correct answer is ", num1*num2
else:
print "That's correct!"
print
x=x+1
def div():
"""
generates and displays the quotient of two numbers, and then prompts the
user to input the correct answer, if the input is incorrect, it then prompts
the user to try again.
[PURPOSE]
"""
x=0
while x<4:
num1 = random.randint(1,20)
num2 = random.randint(1,20)
while (num1%num2!=0):
num2 = random.randint(1,20)
num1 = random.randint(1,20)
print num1, "/", num2, '= ?'
answer = input ('Enter your answer: ')
count1=0
while answer != num1/num2 and count1<3:
count1=count1 +1
print 'Incorrect, please try again.'
print num1, '/', num2, '= ?'
answer = input ('enter your answer:')
if count1==3:
print "Sorry, that's incorrect."
print "The correct answer is ",num1/num2
else:
print "That's correct!"
print
x=x+1
def rand():
"""
picks a arithmetic function at random for the user to to try
[PURPOSE]
"""
num=random.randint(1,4)
if num==1:
add()
if num==2:
sub()
if num==3:
mult()
if num==4:
div()
def main():
"""
main function that brings it all together
[PURPOSE]
"""
show_instructions()
selection = raw_input ('Please select the skill you want to learn: ')
while selection != "q":
if selection == "a":
add()
elif selection == "s":
sub()
elif selection == "m":
mult()
elif selection == "d":
div()
elif selection == "r":
rand()
print "The program will now quit."
quit()
main()`
提前感谢您在此提供的任何帮助！
答案 0 :(得分：5)
您需要将raw_input放在while循环中。
将主要内容更改为：
def main():
"""
main function that brings it all together
[PURPOSE]
"""
show_instructions()
selection = None
while selection != "q":
selection = raw_input ('Please select the skill you want to learn: ')
if selection == "a":
add()
elif selection == "s":
sub()
elif selection == "m":
mult()
elif selection == "d":
div()
elif selection == "r":
rand()
print "The program will now quit."
这里的问题是在{while}循环之前调用raw_input一次。然而，它再也没有被召唤过。相反，循环将继续，但它将继续使用它在selection的第一个（也是唯一的）调用中检索到的相同raw_input值。
此外，您在quit()功能结束时不需要main。你可以让函数返回。虽然这与你的错误无关。
答案 1 :(得分：0)
这将根据随机数和操作产生问题。
from string import lower
from operator import add, sub, mul
from random import randint, choice
ops = { '+': add, '-': sub, '*': mul}
MAXTRIES = 2
def doprob():
op = choice('+-*')
nums = [randint(1,10), randint(1,10)]
nums.sort();nums.reverse()
ans = apply(ops[op], nums)
pr = '%d %s %d = ' % (nums[0], op, nums[1])
oops = 0
while True:
try:
if int(raw_input(pr)) == ans:
print 'correct'
break
if oops == MAXTRIES:
print 'answer\n%s%d'%(pr, ans)
else:
print 'incorrect... try again'
oops = oops + 1
except (KeyboardInterrupt, EOFError, ValueError):
print 'invalid input... try again'
def main():
while True:
doprob()
try:
opt = lower(raw_input('Again? ' ))
except (KeyboardInterrupt, EOFError):
print ; break
if opt and opt[0] == 'n':
break
if __name__ == '__main__':
main()