with open("c:/users/YOUR_USERNAME_HERE/desktop/element_data.txt", "w") as output_file:
  for element_id in solution.all_elements():

    mass = solution.mass(element_id)

    # Average temperature = integral of temperature divided by volume
    temperature = solution.volume_integral("temperature", element_id, time_step=1) / solution.volume(element_id)

    output_file.write(str(element_id) + ", " + str(mass) + ", " + str(temperature) + "\n")