OS. Use Geometry Methods

Type geometry = os.Geometry and then press Return.

This defines the geometry variable as the Geometry group of methods in OpenSTAAD.
Type geometry._FlagAsMethod("GetNodeCount") and then press Return.
This is required to correctly identify the OpenSTAAD methods as such in Python.
Note: This approach is required for this first time you use a method in a python program using OpenSTAAD method. It is not required for each time that method is re-used within the same code.
Type geometry._FlagAsMethod("GetMemberCount") and then press Return.
This is required to correctly identify the OpenSTAAD methods as such in Python.
Note: This approach is required for this first time you use a method in a python program using OpenSTAAD method. It is not required for each time that method is re-used within the same code.

Your program at this point should look like:

from comtypes import automation
from comtypes import client
import ctypes
os = client.GetActiveObject("StaadPro.OpenSTAAD")
geometry = os.Geometry
geometry._FlagAsMethod("GetNodeCount")
geometry._FlagAsMethod("GetMemberCount")