No one said they don't. Just there still are and always will be parts which are computationally heavy but written in python. e.g. pandas map is 300x slower than

No one said they don't. Just there still are and always will be parts which are computationally heavy but written in python. e.g. pandas map is 300x slower than numpy map[1] for the same operation. But not everything could be vectorized and even if some complex function could be vectorized it will involve multiple passes over memory for the same array. [1]: https://www.exxactcorp.com/blog/Deep-Learning/how-to-speed-up-python-pandas-by-over-300x https://www.exxactcorp.com/blog/Deep-Learning/how-to-speed-u...