Psyco is a python module that can improve the speed of some python programs. Psyco can be found here: http://psyco.sourceforge.net.
Pysco has little impact on the speed of the CherryPy code itself (the code is already really fast :-) so you should only use it if you think it can improve the speed of the code that you wrote for your site (for instance, if you use some number-crunching functions to build your pages).
Also, some users reported that Psyco introduces big memory leaks in CherryPy web apps. So if you try to use it and notice that your site leaks memory, you'll know where to look ...
In order to enable Psyco with CherryPy, you should have Psyco installed on your machine and then all you have to do is to use the "initProgram" special function and to put the following code in it:
def initProgram(): import psyco psyco.full()
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