How to make hollow object with only surface into solid? I kept creating a hollow cylinder by spinning a curve [Example]. 
This is the hollow cylinder I made by spinning a second-order polynomial curve. The cylinder would be hollow but not "filled" or not "solid".



After I exported it into STL, it is still hollow. However, I need the cylinder to be solid. So is there a function to spin a surface to make a solid object using python script? If not, is there any other way to do it?
Thank you
It seems to me that you didn't finish the outline before you spun the model, so now you have three options. See the blender documentation for the Spin function.


You can modify your outline to have a top and bottom and re-spin it.
Select Edge Ring and press F to make a face.

2.1 Press Alt+P to Poke the face, thus making a triangle fan.
You can use Grid Fill or from the Ctrl+F menu.