Put the indexnumber that is ture in a list

I have some intersected geometry.
7 doors intersect with 7 walls out of a collection of 20 walls.
So I have 7 listst with 19 occurences of false and one true.
1 wall contains 2 doors.
I want to merge these lists into a single list like the one I created with the codeblock.

Logically this would be a very simple thing: take the indexnumber of true and put it in a list…

Thanks in advance!

Fixed it!

Initially I thought it should be done with a filter by boolean mask.
I had put the outputs in the wrong input.
The mapped list with 7 listst containing 19 falses and 1 true has to go into the mask.
The 20 walls into the filterlist…

This is the logical way to use a boolean mask with list.map.
Too much scripting today I guess…:slight_smile: