> There's a reason most high-performance Python libraries are not written [with Cython], and core routines are just written in C instead. Pandas, Scipy and lxm

> There's a reason most high-performance Python libraries are not written [with Cython], and core routines are just written in C instead. Pandas, Scipy and lxml are large, very popular Python libraries that use Cython. The article even mentions them at the end.