Generally you start with Python and 1) get the code correct (hardest part) and then 2) port the performance critical parts to C/C++. So even they ended up with

Generally you start with Python and 1) get the code correct (hardest part) and then 2) port the performance critical parts to C/C++. So even they ended up with 0% in Python, it wouldn't "look bad". You got the benefit in part 1. (And as others have said, 17% of LOC in Python might still mean majority of the functionality in Python).