Cython is one of a possible number of solutions to the most painful of Python's traits – the lack of efficiency. Large and complex mathematical calculations may be easily coded in Python (much easier than in "C" or any other traditional language), but the resulting code execution may be extremely time-consuming.

How are these two contradictions reconciled? One solution is to write your mathematical ideas using Python, and when you're absolutely sure that your code is correct and produces valid results, you can translate it into "C". Certainly, "C" will run much faster than pure Python.

This is what Cython is intended to do – to automatically translate the Python code (clean and clear, but not too swift) into "C" code (complicated and talkative, but agile).