I work in python all the time, and I’ve still not found a situation where this happened. Sometimes you might have specific components that you might want to write in other languages, but this is really rare unless you’re manually writing really computationally intensive or time critical procedures. Which hopefully you should know going into the project. Like if you’re rolling your own in-line audio processing you know up front that python is a bad choice. But any CRUD-like app? Python is plenty fast, especially if you’re relying on c implementations of heavy-lifting stuff.