Why shouldn't I use PyPy over CPython if PyPy is 6.3 times faster?

Question

I\'ve been hearing a lot about the PyPy project. They claim it is 6.3 times faster than the CPython interpreter on their site.

Whenever we talk about dynamic languag

Answer 1

I did a small benchmark on this topic. While many of the other posters have made good points about compatibility, my experience has been that PyPy isn't that much faster for just moving around bits. For many uses of Python, it really only exists to translate bits between two or more services. For example, not many web applications are performing CPU intensive analysis of datasets. Instead, they take some bytes from a client, store them in some sort of database, and later return them to other clients. Sometimes the format of the data is changed.

The BDFL and the CPython developers are a remarkably intelligent group of people and have a managed to help CPython perform excellent in such a scenario. Here's a shameless blog plug: http://www.hydrogen18.com/blog/unpickling-buffers.html . I'm using Stackless, which is derived from CPython and retains the full C module interface. I didn't find any advantage to using PyPy in that case.