Python stores the data in its appropriate data representation and memory space. However, packages such as NumPy are implemented in systems programming languages such as C, Rust or Fortran. These ...

Today, NumPy is completely open-source and has many contributors. It is also widely regarded as the best Python library for Machine Learning and AI.

As an aside, Python modules and packages that use C libraries (such as NumPy or Cython) are able to avoid the GIL entirely. That’s another reason they’re recommended for a speed boost.