如何在 while 循环中添加计数器？

Question

我有一些代码要求用户猜测计算的答案，然后告诉他们他们是正确的或尝试找出他们出错的地方。我在其中使用了 while 循环，但有时它会卡住，有没有办法为所进行的猜测添加计数器，并在 5 次错误猜测后中断 while 循环？这是到目前为止我的代码的一部分：

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#define correct answer for A\nAc=L*xm\n#ask user to work out A (monthly interest * capital)\nwhile True:\n    A= raw_input("What do you think the monthly interest x the amount you are borrowing is? (please use 2 d.p.) \xc2\xa3")\n    A=float(A)\n    #tell user if they are correct or not\n    if A==round(Ac,2):\n        print("correct")\n        break\n    elif A==round(L*x,2):\n        print("incorrect. You have used the APR rate, whic is an annual rate, you should have used this rate divided by 12 to make it monthly")\n        continue\n    elif A==round(L/(x*100),2):\n        print("incorrect. You have used the interest rate as a whole number when you should have used it as a decimal, and divided it by 12 for the monthly rate")\n        continue\n    else:\n        print("Wrong, it seems you have made an error somewhere, you should have done the loan amount multiplied by the monthly rate")\n        continue\n

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Answer 1

标准库的itertools提供了一个向上计数的迭代器：

import itertools

for i in itertools.count():
    print(i)

您可以设置start和step：

# count(10) --> 10 11 12 13 14 ...
# count(2.5, 0.5) --> 2.5 3.0 3.5 ...

Answer 2

Pythonic方式是

max_guesses = 5
solution = ... # Some solution
guessed = False
for wrong_guesses in range(1, max_guesses + 1):
    guess = ... # Get Guess
    if guess == round(solution, 2):
        print("correct")
        guessed = True
        break 
    ...
else:
    print(f"You have exceeded the maximum of {max_guesses} guesses") 

这样循环就执行了大部分max_guesses时间。else仅当循环因break语句而未结束时（即没有正确猜测时）才会执行该块。

请注意，max_guesses + 1because是区间[low, high)（不包括上限）range上的迭代器。因此，要从 1 运行到 max_guesses，我们必须 +1。

Answer 3

一般来说，它应该看起来像这样：

i = 0
while i < max_guesses:
    i+=1
    # here is your code