如何在用户输入不正确的值后使python循环程序?

Question

为class赋值，我需要用户输入1到500之间的值，如果用户输入不正确的值超过三次，那么程序应该关闭。我也有问题，使程序循环，如果用户需要再次尝试

这是我到目前为止写的。

flour = 2.75
baking_soda = 1
baking_powder = 0.5
butter = 1
sugar = 1.5
egg = 1
vanilla = 1
makes = 48

cookies = float(input('Enter number of cookies: '))

count = 0

flour = (cookies * flour) / makes
baking_soda = (cookies * baking_soda) / makes
baking_powder = (cookies * baking_powder) / makes
butter = (cookies * butter) / makes
sugar = (cookies * sugar) / makes
egg = (cookies * egg) / makes
vanilla = (cookies * vanilla) / makes

while (cookies >=1 and cookies <=500):
print("You need " + str(round(flour,2)) +
" cups of flour, " + str(round(baking_soda,2)) +
" teaspoons of baking soda, " + str(round(baking_powder,2)) +
" teaspoons of baking powder, " + str(round(butter,2)) +
" cups of butter, "+ str(round(sugar,2)) +
" cups of sugar, " + str(round(egg,2)) +
" eggs and " + str(round(vanilla,2)) +
" teaspoons of vanilla.")
break
count=0
while (cookies <1 or cookies >500):
count+=1
cookies = float(input('Enter valid number: '))
if (count>=3):
print("I will now close.")
exit()

Answer 1

这是它现在的样子，我想这就是答案了，因为它不再给我任何问题。

flour = 2.75
baking_soda = 1
baking_powder = 0.5
butter = 1
sugar = 1.5
egg = 1
vanilla = 1
makes = 48
cookies = int(input('Enter number of cookies from 1 to 500: '))
count=0
while (cookies <1 or cookies >500):
count+=1
cookies = int(input('Enter valid number: '))
if (count>=3):
print("I will now close.")
exit()
while (cookies >=1 and cookies <=500):
flour = (cookies * flour) / makes
baking_soda = (cookies * baking_soda) / makes
baking_powder = (cookies * baking_powder) / makes
butter = (cookies * butter) / makes
sugar = (cookies * sugar) / makes
egg = (cookies * egg) / makes
vanilla = (cookies * vanilla) / makes

print("You need " + str(round(flour,2)) +
" cups of flour, " + str(round(baking_soda,2)) +
" teaspoons of baking soda, " + str(round(baking_powder,2)) +
" teaspoons of baking powder, " + str(round(butter,2)) +
" cups of butter, "+ str(round(sugar,2)) +
" cups of sugar, " + str(round(egg,2)) +
" eggs and " + str(round(vanilla,2)) +
" teaspoons of vanilla.")
break

Answer 2

您的想法是正确的，但是您需要考虑循环的流程。请求用户输入总是很棘手的，你总是想在做任何计算或工作之前尝试验证输入。

有几件事你似乎已经明白了，你需要至少问一次。您可以像下面这样在单个循环中完成所有这些操作。

我基本上是在创建一个无限循环，只有当你出错5次时才会停止。请注意，除非用户至少有一次做对了，否则循环不会继续进行计算。请注意，在现实世界中，您将为用户提供一个随意退出的机会。试着用这样一种方式来实现它:如果用户输入字母q，程序就结束。

请注意，我留下了一个小错误让你修复。如果你能解决它，你就会得到循环的句柄。尝试输入2个cookie，然后输入48个cookie。看看这个数字为什么不合理，有几种方法可以解决这个问题，但关键是要理解为什么会出错。

flour = 2.75
baking_soda = 1
baking_powder = 0.5
butter = 1
sugar = 1.5
egg = 1
vanilla = 1
makes = 48
count = 0
while (True):
cookies = float(input('Enter number of cookies: '))

if (cookies < 1 or cookies > 500):
print('Invalid response, the number must be between 1 and 500')
count += 1

if count > 4:
print("I will now close.")
break
continue

flour = (cookies * flour) / makes
baking_soda = (cookies * baking_soda) / makes
baking_powder = (cookies * baking_powder) / makes
butter = (cookies * butter) / makes
sugar = (cookies * sugar) / makes
egg = (cookies * egg) / makes
vanilla = (cookies * vanilla) / makes

print("You need " + str(round(flour,2)) +
" cups of flour, " + str(round(baking_soda,2)) +
" teaspoons of baking soda, " + str(round(baking_powder,2)) +
" teaspoons of baking powder, " + str(round(butter,2)) +
" cups of butter, "+ str(round(sugar,2)) +
" cups of sugar, " + str(round(egg,2)) +
" eggs and " + str(round(vanilla,2)) +
" teaspoons of vanilla.")