psyco snapshot
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              High-level languages need not be slower than low-level ones.

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Psyco is a Python extension module which can greatly speed up the execution of any Python code.


12 March 2012

Psyco is unmaintained and dead. Please look at PyPy for the state-of-the-art in JIT compilers for Python.

16 July 2010

Python 2.7 is unsupported so far. Anyone interested in porting Psyco to it is welcome. I started the work in a branch but it needs finishing.

4 March 2010

On Mac OS/X "Snow Leopart" you don't actually need to recompile Python yourself, but just use the following command line (thanks Elvis Pfützenreuter):

defaults write Prefer-32-Bit -bool yes

8 December 2009

Just for reference, Psyco does not work on any 64-bit systems at all. This fact is worth being noted again, now that the latest Mac OS/X 10.6 "Snow Leopart" comes with a default Python that is 64-bit on 64-bit machines. The only way to use Psyco on OS/X 10.6 is by recompiling a custom Python in 32-bit mode (on Linux, see here or here for example).

20 January 2009

Michael Foord contributed a Windows binary for Python 2.6 (as well as Psyco 1.5.1 binaries for Python 2.2 and 2.3). Get them directly from

7 January 2008

Thanks Chaiwat Suttipongsakul for contributing a Win32 binary for Python 2.5! Get it from the downloads page.

16 December 2007

Released Psyco 1.6 with Intel MacOS/X support, thanks to Gary Grossman. Also includes a couple of general bug fixes (Windows binaries: contribution welcome). From this version onwards we no longer support Pythons older than 2.2.2.

28 September 2007

Sorry, the file at was missing for a while. It's back now.

26 September 2007

Psyco was ported to Intel Mac OS/X by Gary Grossman. I will review and check in his code; in the meantime the patch is available there:

2 May 2007

The snake machine is down - died of too much PyPy - so the snapshot of the latest sources is now at . See installing from sources.

26 January 2007

Fixed a bug triggered by Python 2.5's bytecode optimizer. Users of 2.5 should either avoid psyco.profile() or upgrade to the subversion head.

8 December 2006

Got a Win32 binary for Python 2.4. See downloads. Contributed by ffao.

29 November 2006

Fixed the corrupted Win32 binary for Python 2.5. See downloads. Thanks again to Jon Foster. The corruption of binary files attached to SourceForge's patch tracker seems to be a known problem... (Note that as far as I can tell, mirrors make take a little while before they have got the updated version. The correct version has an MD5 sum of 14194043a1488c7a33ad7f4ba7c2171c.)

27 November 2006

The Win32 binary installer seems to be broken :-( Updates to follow...

22 November 2006

Got a Win32 binary for Python 2.5. See downloads. Thanks Jon Foster!

21 November 2006

Released Psyco 1.5.2 with Python 2.5 support. (Windows binaries: contribution welcome.)


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This site has been last updated Fri, 16 Jul 2010.

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