Yes, that's the case for most data scientists, and often for users in general. You can get pretty good performance levels from Python by delegating to C correctly. Even end users tend to do that because the data science stack of Python (numpy and the many libraries using it) spend almost all of their runtime in C routines.

If you are using Numpy correctly (even with little understanding of Python itself and its C-API) then virtually all your hot loops are executed in optimal C code.