This has one big backdraw however. Not only do you need to write in two different languages, the rewriting in C requires a lot of care, as the language protects you much less than the high level language you implement for.
One big attraction of Go is, that it is high level and productive enough, to be the main implementation language, and for time critical stuff very efficient. So you don't have to cross language bareers to implement speed critical code and you get the full type and memory safety in the whole stack.
Interestingly, one can write Python extensions in Go, so in most cases that would be my choice these days for speeding up critical code paths in Python.