Login User

def login():
    print("Login")
    username = input("Username: ")
    password = input("Password: ")
    if user_exists(username, password):
        print(f"Welcome {username}")
    else:
        print("Invalid User")


def user_exists(username, password):
    with open('user.txt') as f:
        users = f.readlines()
        exists = False

        for user in users:
            if username in user:
                exists = True
                break
        return exists


if __name__ == "__main__":
    login()