[PyMOL] Question about Iterate and Edit-Mode

[Martin H. <ma...@bl...>]

Dear All
I am trying to get behind the way 'iterate' works, since I see it quite 
frequently in PyMOL scripts.
The example in the help page is a bit limited in the sense that I cant 
explain to myself what actually is happening.

Say, if I were to write the functionality of 'iterate' using a for-loop, 
how would this for-loop look like?
Something like this maybe?

for i in selection:
     i.expression()

I'm a bit confused about what can go into 'expression'.

The second question is related to the Edit-Mode of PyMOL. When I switch 
to Edit-Mode and click on a atom, a couple of states/objects (?) appear 
in the object list: pk1, pkmol, pkresi, pkchain, pkobject.
What do these objects mean? What are they useful for? I'm sure there is 
a reason for them, but I cant figure it out.

Thanks a lot for your help guys.

Martin