Python：如何将 for 循环和 while 循环组合在一起？

Question

我试图创建一个注册 function ，它将提示用户少数信息。 下面的代码是 function 的部分代码。 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 循环检查已注册的 email。 但是，当注册 email 已注册时，我正在使用递归 function ，有没有办法可以避免递归 ZC1C425268E68385D1AB5074C17A94F14 并将 for 循环放入循环中？

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()               
               

Answer 1

不要使用递归。 这样的事情会做。 您的主要问题是for循环。

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()