def data_network():

    """Verify logins for members-only network. """

    # This version has 10 users.  You can change the number by changing the
    # three tables and changing the value in the range statement of the
    # for loop.

    print("\n\tExclusive Computer Network")
    print("\t\tMembers only!\n")

    users = ["George Washington",
             "John Adams",
             "Thomas Jefferson",
             "James Madison",
             "James Monroe",
             "John Quincy Adams",
             "Andrew Jackson",
             "Martin Van Buren",
             "William Henry Harrison",
             "John Tyler"]

    nicknames = ["George",
                 "John",
                 "Tom",
                 "Jemmy",
                 "James",
                 "Quincy",
                 "Old Hickory",
                 "OK",
                 "Doc",
                 "Tippecanoe"]
                 

    passwords = ["cherry tree",
                 "Hamilton",
                 "Sally",
                 "Dolly",
                 "Doctrine",
                 "one term",
                 "New Orleans",
                 "Dutch",
                 "pneumonia",
                 "Texas"]

    levels = [5,4,5,5,4,4,3,2,2,2]
   
    security = 0
    found_user = False

    username = ""
    while not username:
        username = input("Username: ")

    password = ""
    while not password:
        password = input("Password: ")

    for i in range(10):
        if username == users[i]:       # Found user.  Now check password.
            found_user = True          # So we know whether we even found the user in the db.
            if password == passwords[i]:
                security = levels[i]
                print("Welcome, ", nicknames[i])
            else:
                print("Sorry, you don't know the password.")  # Security stays 0.
            break                	  # Exit the loop now.
    # If the user was in the db, we found him/her.
    if found_user:
        # This is where we'd print a message that would depend on
        # security level.
        pass        # This does nothing.  It's here as a placeholder because a statement
                    # is required.  Get rid of it when something real goes here.
    else:
        print("Apparently you don't exist.")