def intro():
    print("\nEnter your details to login \n")


def login():
    # Opens the user.txt file
    with(open('uid.txt', 'r+')) as u_name:
        a = u_name.read()
        uid = a.split()
        uid_low = [item.lower() for item in uid]

    # Opens the passwords.txt file
    with(open('pwd.txt', 'r+')) as u_pass:
        a = u_pass.read()
        pwd = a.split()

    # Takes user input
    u = input('Enter your username: ')
    u1 = u.lower()
    p = input('Enter your password: ')
    bo = False

    if u1 in uid_low:
        bo = True

    '''Checks if user exists or not'''
    if bo is True:
        bo = True
    else:
        print('User does not exist')

    '''Finds the index of user'''
    i = uid_low.index(u1)

    '''Checks if password is correct or not'''
    if p == pwd[i]:
        print('Welcome', u)
        print('Successfully logged in. ')
    else:
        m = 3
        n = 3
        while p != pwd[i]:
            print("Password doesn't match \n")
            print('You have', n, 'tries left.')
            n -= 1
            p = input('Re-enter your password: ')
            if p == pwd[i]:
                print('You entered incorrect passwords', m - n, 'times.\n')
                print('Successfully logged in. Welcome', u)
                break