# Get residue position from Pymol Selection

I can make a selection in Pymol using the resi parameter. Is there a way to get this resi data back out of a selection object? The only thing I found so far is how to get the position, as in the x/y/z coordinates from a selection.

For context, I have a table with a set of data points for each residue in the amino acid sequence of the displayed structure and I want to write a function where I can print the data based on the current selection. So my thought would be something like the following, where the content of the 'get_residue_positions_for_selection' function would be what I'm asking about.

def show_selection_position_data():
residue_data = {
, "1": ['high', 0.1]
, ...
}
selections = cmd.get_names('selection')

if sele not in selections:
print("No selection")
return

residues = get_residue_positions_for_selection("sele")

for residue in residue_selections:
print(residue_data[residue])

return

• This certainly a very interesting question and a cool answer. The advice I was given (to pretty much the same problem) was to use Pymol scripting directly rather than via Python.
– M__
Jun 14 '19 at 22:48

Ok, after some more searching I found the answer.

You have to use the cmd.iterate function to iterate over the default selection ("sele", first parameter). With the second parameter you can push the variables you need into an array for later access. In this case I wanted the residue number so I used the variable 'resv'. A full list of the variables exposed by the iterate function can be found on the pymolwiki

Note that you can use a function call as the second parameter and if you need a more complex selection than 'sele' you can use selector.process in the iterate function.

Here is my final working function. Note that I used a set for storing the residue ids, since the iterate function technically iterates over the atoms and so the same residue will likely appear multiple times in your selection.

def show_selection_position_data():
residue_data = {
, 1: ['high', 0.1]
, 2: ['high', 0.2]
, 3: ['low', 0.1]
, 4: ['high', 0.05]
, 5: ['middle', 0.2]
, 6: ['high', 0.1]
, 7: ['high', 0.1]
}
selections = cmd.get_names('selections')

if "sele" not in selections:
print("No selection")
return

userSelection = "sele"

stored.residues = set()