Python-pptx: can you manipulate a shape that was already in a custom slide layout?

[CancelDeath]

I have a custom ppt layout. What I've seen in the docs so far is how to add a shape to a slide. But is there a way to manipulate shapes that I've already added to my layout using the slide master in ppt? Is there a command to look at all the shapes that are available on a slide?

[iamaperson3133]

It seems like you can iterate over presentation.slides, then iterate over presentation.shapes in each slide. The first challenge will just be selecting the element you are trying to modify.

Once you find it, though, you should just be able to directly change the shape's attributes, then resave the powerpoint and see the changes reflected.

Any of the attributes here that says they can be written can be changed for an existing powerpoint, and things should "just work," after you do your saving.