Why am I receiving ERROR 404 – when attempting to use Python Flask

@app.route("/") # I think you have missed this.

# Set up Postgres database connection and cursor.
t_host = "PostgreSQL database host address" # either "localhost", a domain name, or an IP address.
t_port = "5432" # default postgres port
t_dbname = "database name"
t_user = "database user name"
t_pw = "password"
db_conn = psycopg2.connect(host=t_host, port=t_port, dbname=t_dbname, user=t_user, password=t_pw)
db_cursor = db_conn.cursor()

def import_temp():
def import_temp():
    # Do something