我的登錄方法未在我的register（）中調用，並且在mainError（0）中出現我的錯誤，當不應該這樣做時

Question

這是我的代碼：

import time

print("Welcome to the quiz")

print("Would you like to login with an existing account or register for a new account?")

def login():
    userQ = input("Please enter your username: ")
    passQ = input("Please enter your password: ")
    #In progress of making...

def register():
    print ("Your username will now be created from your first name and age.")
    fname = input("Please enter your first name: ")
    age = input("Please enter your age: ")
    fname2 = fname[:3]
    username = fname2 + age
    print ("Your username is {}".format(username.upper()))
    password = input("Please enter a password for your new account: ")
    time.sleep(1.0)
    print ("Username: {}".format(username))
    print ("Password: {}".format(password))
    with open("UserPass.csv", "w") as f:
        for line in f:
            file = line.split(",")
            f.write(username) in file[0]
    print ("ACCOUNT CREATED")
    login()

class validation(Exception):

    def __init__(self, error):
        self.error = error

    def printError(self):
        print ("Error: {} ".format(self.error))

def mainError():
    try:
        raise validation('Please enter a valid input')
    except validation as e:
        e.printError()

def Menu():
    while True:
        options = ["Login", "Register"]
        print("Please, choose one of the following options")
        num_of_options = len(options)
        for i in range(num_of_options):
            print("press " + str(i + 1) + " to " + options[i])
        try:
            uchoice = int(input("? "))
            if uchoice == 1:
                print("You chose to " + options[uchoice - 1])
                login()
                break
            elif uchoice == 2:
                print("You chose to " + options[uchoice - 1])
                register()
                break
            elif (uchoice - 1) > len(options):
                mainError()
        except ValueError:
            mainError()

Menu()

在我的代碼中，如果用戶選擇注冊一個新帳戶，它將運行“ register（）”方法。 在用戶輸入方法中的用戶名和密碼后，它將其寫入csv文件，然后調用login（）方法。 但是，相反...它以某種方式運行Menu（）方法，並忽略了我的login（）。

另外，到達register方法的末尾后，它會打印一條錯誤消息，該錯誤消息是我不希望的'Class Validation（Exception）和'mainError（）'產生的-我不知道為什么它這樣做是因為我還沒有調用mainError（）。

我運行代碼並選擇注冊的示例：

Welcome to the quiz
Would you like to login with an existing account or register for a new account?
Please, choose one of the following options
press 1 to Login
press 2 to Register
? 2
You chose to Register
Your username will now be created from your first name and age.
Please enter your first name: Siddharth
Please enter your age: 16
Your username is SID16
Please enter a password for your new account: shamrock
Username: Sid16
Password: shamrock
Error: Please enter a valid input 
Please, choose one of the following options
press 1 to Login
press 2 to Register
? 

如您所見，在注冊之后，在不需要之前，它轉到Manu（）而不是login（），並顯示“錯誤：請輸入有效的輸入”。

我怎樣才能解決這個問題。 謝謝！

Answer 1

更改

with open("UserPass.csv", "w") as f:
    for line in f:
        file = line.split(",")
        f.write(username) in file[0]

至

with open('UserPass.csv', 'a') as f:
    f.write('whatever text you want to save')