Python：如何将for循环和while循环结合在一起？

杰克逊·泰

我试图创建一个注册功能，它将提示用户少信息。下面的代码是函数的一部分。我正在使用 while 循环来防止任何无效输入或特定输入来执行其他任务。输入验证完成后，我使用 for 循环来检查注册的电子邮件。但是，当注册电子邮件已被注册时，我正在使用递归函数，有没有办法可以避免递归函数并将 for 循环放在 while 循环中？

user = [['a','a.gmail.com'],['b','b.gmail.com'],['c','c.gmail.com']]

def signup():
     print("\ Enter '0' to return mainpage")
     emailAddress = input("Please enter your email address   : ")
     while True:
          if emailAddress == '0':
               print('mainpage returned')
               signup()
          elif emailAddress == '':
               emailAddress = input("Please enter your email address   : ")
          else:
               break
     # check if email address is registered or not
     for item in user:
          if emailAddress == item[1]:
               print("This Email address has been registered")
               signup()
     else:
          print("email registering:",emailAddress)
signup()

丹尼尔·F

不要使用递归。像这样的事情会做。您的主要问题是for-loop。

user = [['a','a.gmail.com'],['b','b.gmail.com'],['c','c.gmail.com']]

def signup():
    
    emailAddress = None
    
    #---
    
    while True:
        print("\ Enter '0' to return mainpage")
        
        desiredEmailAddress = input("Please enter your email address   : ")
        
        if desiredEmailAddress == '0':
            print('Ok, will return to mainpage')
            break # <---- BREAK OUT OF THE WHILE LOOP
        
        elif desiredEmailAddress == '':
            pass # let the while-loop iterate again
        
        else:
            # check if email address is registered or not
            emailIsAlreadyRegistered = False
            
            for item in user:
                if desiredEmailAddress == item[1]:
                    emailIsAlreadyRegistered = True
                    break # we can break out of the for loop
            
            if emailIsAlreadyRegistered:
                print("This Email address has been registered")
                pass # let the while-loop iterate again
            else:
                emailAddress = desiredEmailAddress
                break # <---- BREAK OUT OF THE WHILE LOOP
    
    #---
    
    if emailAddress is None:
        # User wanted to return to mainpage
        return None
    else:
        print("email registering:", emailAddress)
        return emailAddress
    
signup()

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