Hi Alessio,
ChimeraX does not read Chimera session files (.py).  However, if you start from Chimera, you can save your project as a file to open ChimeraX. 

In Chimera, choose menu File... Export Scene, then choose file type: ChimeraX (also .py but is different than a Chimera session).  See Chimera help:
<https://www.rbvi.ucsf.edu/chimera/docs/UsersGuide/export.html>

Then you can exit Chimera, start ChimeraX, and open the file you just saved (ChimeraX "open" command or menu: File... Open).

This export does not include every type of data, though -- from the help link above:

 "includes atomic models, molecular surfaces, volume models (surface, mesh, image, plane/orthoplane, and box renderings), per-model clipping, sequences and sequence alignments, 2D labels and arrows, and color key. Not supported: per-vertex colorings of surfaces (e.g., by value, distance, or zone), nucleotide representations, worms, other types of surface models, etc."

So if you had nucleotide representations, worms, or special surface colorings, you may have to regenerate them in ChimeraX.

I hope this helps,
Elaine
-----
Elaine C. Meng, Ph.D.                       
UCSF Chimera(X) team
Resource for Biocomputing, Visualization, and Informatics
Department of Pharmaceutical Chemistry
University of California, San Francisco

> On Aug 27, 2024, at 8:26 AM, Alessio Nocentini via ChimeraX-users <chimerax-users@cgl.ucsf.edu> wrote:
>
> Dear Elaine,
>
> I have another doubt. How do I open a Chimera project in ChimeraX. Is it possible?
>
> Thank you for the support
>
> best
>
> Alessio
>