整数，输入，prin

Question

我的主要问题是打印，它不工作，因为它给我的错误：

NameError; the name 'ask2' is not defined

我是Python的绝对初学者，因此我完全不知道如何使它成为全局的，或者在这些行中做些什么。你知道吗

ask = input("-Would you like to 1 input an existing number plate\n--or 2 view a random number\n1 or 2: ")
if int(ask) == 1:
    print("========================================================================")
    ask2 = ""
    while ask2 != 'exit':
        ask2 = input("Please enter it in such form (XX00XXX): ")).lower()
        # I had no idea that re existed, so I had to look it up.
        # As your if-statement with re gave an error, I used this similar method for checking the format.
        # I cannot tell you why yours didn't work, sorry.
        valid = re.compile("[a-z][a-z]\d\d[a-z][a-z][a-z]\Z")
        #b will start and end the program, meaning no more than 3-4 letters will be used.
        # The code which tells the user to enter the right format (keeps looping)
        # User can exit the loop by typing 'exit'
        while (not valid.match(ask2)) and (ask2 != 'exit'):
            print("========================================================================")
            print("You can exit the validation by typing 'exit'.")
            time.sleep(0.5)

            print("========================================================================")
            ask2 = input("Or stick to the rules, and enter it in such form (XX00XXX): ").lower()
            if valid.match(ask2):
                print("========================================================================\nVerification Success!")
                ask2 = 'exit'  # People generally try to avoid 'break' when possible, so I did it this way (same effect)
            # This 'elif' is optional, it just provides a bit better feedback to the user so he knows he manually stopped
            elif ask2 == 'exit':

        #There are other parts of the code, but it's not necessary

else:
    plate = ""
    # This randomly adds two capital letters (your own code)
    for i in range(2):
        plate += chr(random.randint(65, 90))
    print()
    print(plate)

print("The program, will determine whether or not the car "+str(plate),ask2+" is travelling more than the speed limit")

Answer 1

您的代码当前的结构如下：

if some_condition:
    ask2 = ''
else:
    ...
print(ask2)

问题是当some_condition是False并且else块执行时，在if/else之后，当您尝试打印ask2时，您得到的是NameError，因为if块从未运行，而且ask2未定义。你知道吗

你需要做：

ask2 = ''
if some_condition:
    ...
else:
    ...
print(ask2)

另外，这是不相关的，但是使用break绝对没有错。你知道吗

Answer 2

这个错误确实很好地说明了这一点。ask2似乎没有定义。你知道吗

你以前在什么地方定义过int吗？如果您以前没有在某个地方声明过它，您将无法使用它。你知道吗

if int(ask) == 1:
    print("========================================================================")
    ask2 = ""
    while ask2 != 'exit':

你好像在呼吁“ask2存在！='退出''，但您没有给它赋值。它只是说ask2=“。尝试在之前给它赋值，要么定义它，要么自动赋值。你知道吗