Python is really widespread, but at least in my company it's used for analysis and prototyping only. Then the prototype is ported either to Java, C# or C++.
I don't know if it's common practice, but we work like that and totally makes sense to us.
Depends on the organizations needs, for what we work on performance does not matter terribly much, thus a MVP in Flask is often cleaned up and put up on Gitlab (with a Github mirror) once its vaugely usable.
I don't know if it's common practice, but we work like that and totally makes sense to us.