Whilst that is true, for data science related things I end up using Pandas (and Numpy) often which are fast.
So most of the heavy lifting is not done by python itself.
So most of the heavy lifting is not done by python itself.
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.
So you will write Python, but get very good resource (both time and space) efficiency.