Function that is not running correctly

simulation_function

def simulation():
    """
    Main simulation function.
    :return:
    """
    rowNum = 1
    day = 1

    number_humans = session.query(Humans).count()
    number_vectors = session.query(Vectors).count()

    clear_screen()

    print("Currently running simulation. This will take a while. \nGrab some coffee and catch up on some reading.")
    sleep(5)

    try:
        for d in range(days_to_run):  # TODO: Finish this next.
            exposures = 0

            #for h in range(number_humans):  # Select each human by id
            #row = session.query(Humans).filter_by(id=h)  # TODO:  handle situations where h doesn't match any ID
            row = session.query(Humans).yield_per(1000)  # This might be way more efficient than querying each id
            for r in row:
                i = 0

                if rowNum % 100 == 0:  # Status indicator
                    clear_screen()
                    print("***Python Epidemiological Simulator***\n\n"
                          "   Status: Simulation running \n"
                          "   Current Day: {0} \n"
                          "   Current Exposure Count: {1} \n"
                          "   {2} of {3} Contacts Scanned".format(day, exposures, rowNum,
                                                                  days_to_run*number_humans*contact_rate))

                while i < contact_rate:  # Infect by contact rate per day
                    # Choose any random number except the one that identifies the person selected, 'h'
                    pid = random.randint(1, number_humans)
                    while pid == r.id:
                        input("Identical PID")
                        pid = random.randint(1, number_humans)

                    contact = session.query(Humans).filter_by(id=pid).first()

                    # If human_a is susceptible & human_b is infected, human_a becomes exposed
                    if contact.infected == 'True' and r.susceptible == 'True':
                        exposures += 1
                        #print("*Exposure Count: {0}".format(exposures))
                        row.update({"exposed": 'True'}, synchronize_session='fetch')
                        row.update({"susceptible": 'False'}, synchronize_session='fetch')

                    # If human_b is susceptible & human_a is infected, human_b becomes exposed
                    elif r.infected == 'True' and contact.susceptible == 'True':
                        exposures += 1
                        #print("*Exposure Count: {0}".format(exposures))
                        # contact.update({"exposed": 'True'}, synchronize_session='fetch')
                        # contact.update({"susceptible": 'False'}, synchronize_session='fetch')
                        contact.exposed = 'True'
                        contact.susceptible = 'False'

                    i += 1
                rowNum += 1
            session.commit()
            day += 1

        # TODO: human within 'range' of mosquito - chance of infection
    except KeyboardInterrupt:
        clear_screen()
        input("You interrupted me. Going back to main menu.")
        main_menu()