[PyMOL] Write the number of molecules for each state in a file

[ABEL S. <Ste...@ce...>]

Hello PyMOLers

I have PDB file that contains different frames ( or state or models) extracted from a MD simulation and I would like to select the number the water near (say 3.5 Angstroms) a protein for each state and write the results in the file.

For instance like this where resid is a list of the water that satisfy the cut off below

Frame 0 : residX, residY, ...., 
Frame 1:  residZ, residY, ...., 

In the pml script I have selected the water molecules near the protein within the pymol commands below

### 

select GrA_Channel, (id 1-267+277-542) and name CA+C+O+N
select water_channel, resname SOL within 3.5 of GrA_Channel

f=open("toto.txt","w")

iterate_state 0, water_channel, state + ':' + water_channel ")   ## How to use this command

f.close()

but I do not know to use the iterate_state for each frame with above selected command

Can you help me ?

Thank you in advance

Stéphane