Are any of those examples successful open-source projects with both the computation and the GUI written in Python? I don't know of anything in any field like that.
I think you misunderstood me. The choice of tools for front and backend have to be independent. The only really successful projects implemented in one language are all in C++, and that's difficult for everyone to approach.
I may be confused as to what you mean by GUI in this context. If you are talking about a data exploration GUI... many, many scientists and physical science engineers use Jupyter/JupyterLab as a frontend for data exploration. This largely replaces the need for something like matlab.
If you are talking about practical implementation of those models, I have seen many non open source projects use those backends (things like pandas, sklearn, etc.) with things like django or flask as a frontend.
I think you misunderstood me. The choice of tools for front and backend have to be independent. The only really successful projects implemented in one language are all in C++, and that's difficult for everyone to approach.