.pyx files are python extension files that are used by python to interact directly with the C API. This consequently gives code a massive speedup. A typical .pyx file is translated into C (as a .c file) and then compiled with a C compiler into a .so file on Mac/Linux or .pyd file in Windows. This creates a dynamically-linked-library that python can use.

The .pyx File Extension

Install Cython with `pip install cython`. A suitable C compiler must also be installed before Cython extension modules can be built.

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Cython is an optimizing compiler that allows computationally expensive Python code to be translated into C and compiled for use within a python program. It contains a Python-like syntax as well as static typing. The main performance gain comes from Cython being able to bypass the CPython API (Where python code is interpreted from). 

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