Login Module Help - Comparing data in a text file to data held in a variable

[KeziaKar]

def existingUser():
    userID = input("Please enter your username: ")
    password =input("Please enter your password: ")
    for line in open("database.txt","r").readlines():
        loginDetails = line.split()
        csv1= csv.reader("database.txt", delimiter = ',')
    if userID == loginDetails[0] and password == loginDetails[1]:
        print("Welcome "+(userID))
    else:
        create=input("You do not have an account, would you like to create one?")
        if create == "Yes":
            newuser()
        else:
            end()
    home= input("Hello" +(userID) + "Would you like to """"
    1: enter homework task
    2: check your progress""")
    if home == "1":
        homework()
    elif home =="2":
    
            
        print("Incorrect password")
    return False 

def newUser():
    databasefile = open("database.txt","a")
    userID = input("Enter your username")
    #this checks the password is valid
    incorrectPass= False
    while not incorrectPass:
        password= (input ("Enter a password between 5 to 8 characters"))
        length = len(password)
        if len(password) <3 or len(password)> 9:
            print("Sorry, password must be between 5-8 characters, your password is only ", length, " characters long")
        else:
            #setflag for strength test
            lowerCase =0
            upperCase =0
            digitCase=0


            for ch in password:

                if ch.islower():
                    lowerCase =1
                if ch.isupper():
                    upperCase= 1
                if ch.isdigit():
                    digitCase= 1
            #Strength output
            passwordStrength = upperCase + lowerCase + digitCase
            if passwordStrength ==1:
                print("This is a weak password")
            elif passwordStrength==2:
                print("This is a medium password")
            if passwordStrength ==3:
                print("This is a strong password")
            incorrectPass= True

    FirstAlevel= input("Enter first A-level")
    SecondAlevel=input("Enter second A-level")
    ThirdAlevel=input("Enter third A-level")
    logindata= open("database.txt", "a+")

    line= databasefile.write(userID +"," + password + "," + FirstAlevel+ "," + SecondAlevel + "," + "," + ThirdAlevel + "\n")
    databasefile.close()
    print("Welcome " + (userID) + ", your account has been created, would you now like to..")
    login=input("1.Login 2.Quit")
    if login == "2":
        sys.exit(0)
    elif login =="1":
        main()

def end():
    sys.exit(0)

def main():

    #These are the two options available
    print("Welcome to MyOnline Homework Diary")
    print("-----------------------------------")
    signIn = (int(input("""Would you like to...
    1: Register
    2: Sign In""")))
    if signIn == 1 :
        newUser()
    elif signIn ==2 :
        existingUser()
    else:
        print ("See you later!")
main()
       
       

My code is not allowing any users that have already created an account to sign in and I am not sure why as I am using the csv function to split and read the file but the code is not comparing whats in the text file to the data inputted.