login system user exist in textfile python

def loginExisting():
    userDataEntry = open('loginInfo.txt', 'r')
    listLines = userDataEntry.readlines()
    userDataEntry.close()

    userDict = {}

    for eachLine in listLines:
        entry = eachLine.split()
        username = entry[0]
        password = entry[1]
        userDict[username] = password

    checker = 0
    while(checker == 0):
        print("\nYou've registered already? (OwO) Okay then!\n")
        usernameInput = input("Please enter your username:")
        passwordInput = input("Please enter your password:")


        if(usernameInput in userDict):
            if(userDict[usernameInput] == passwordInput):
                print("\nLogin successful!\nWelcome back,", usernameInput)
                checker = 1

            else:
                print("Password is incorrect. Try again.")
                checker = 0

        else:
            print("Username does not exist. Try again.")
            checker = 0

    nextStep = int(input("\nWould you like to:\n1.) Exit\n2.) Log out and return to menu\n\n"))
    if(nextStep == 1):
        print("\nGoodbye!")

    if(nextStep == 2):
        print("\nReturning to menu...\n")

        return nextStep