python - 未绑定(bind)本地错误: local variable "tries" referenced before assignment

Question

我对编程非常陌生，并且让自己陷入了困境。尝试编写一个简单的猜数字游戏，仍然很粗糙，但我收到一个错误，我不知道如何修复。

这是代码:

随机导入 猜测= 0 print "你必须猜一个 1 到 20 之间的随机数"

def main():
    guessestaken = 0
    number = random.randint(1,20)
    guess = 0
    while guess != number:

        print ("Take a guess")
        guess = input("Your guess: ")
        guess = int(guess)
        guessestaken = guessestaken + 1
        if tries is None:
            tries = 0
        tries = tries + 1



        if guess < number:
            print "Too low, try again"

        if guess > number:
            print "Too high"


        if guess is number:
            print "Well done, you guessed the number in ", guessestaken, "guesses."


#        if guess != number:

x = 1
while x is 1:
#    if tries is 3: break
    guessestaken = 0
    main()

之后我收到此错误:UnboundLocalError:分配之前引用了局部变量“tries”，任何帮助将不胜感激。

Answer 1

您无法检查 undefined variable 是否None:

def main():
    while True:
        if tries is None:
            tries = 0
        tries = tries + 1

相反，您应该预先定义它

def main():
    tries = 0

    while True:
        tries = tries + 1

您可以使用以下命令检查变量是否已定义

try:
    tries
except NameError:
    tries = 0

但是我绝对建议不要这样做。总有一种方法可以确保变量被定义，而不确定变量是否被定义的代码设计得很糟糕。