I myself couldn't find any information on this when I tried to get it, but I by accident met somebody who managed to get it to build - what I'm referring to is irssi-python.

First, get irssi-python from the Subversion repository over at [http://svn.irssi.org/repos/irssi-python/] (http://svn.irssi.org/repos/irssi-python/), then fetch your current Irssi version's sources. They're available on irssi.org, and unpack it.

Next, you need to build irssi-python, which probably is the hardest project to build that I've ever managed to get built. In fact, so hard that I needed to write a script to build it for me, as follows:

#!/bin/bash
svn revert -R . &&
sed -i 's/ docs//' Makefile.am &&
sed -i 's|docs/Makefile||' 'configure.in' &&
sed -i 's/pyconstants.c/pycore.c/' 'configure.in' &&
cp /usr/share/aclocal/ac_python_devel.m4 . &&
libtoolize -f -c &&
aclocal --force -I. &&
autoheader -f &&
autoconf -f &&
automake -a -c --gnu --foreign &&
./configure --with-irssi="$1"  &&
make -C src constants &&
make  &&
echo -e "\n\n***\nAll done!"

Save that in the irssi-python directory, and make sure you have autoconf-archives installed (Gentoo: emerge autoconf-archives), then run it with the path to the Irssi source as the sole argument:

chmod u+x ./toxik-make.sh
./toxik-make.sh ../irssi-0.8.12

Then, when built:

sudo make install

The module will be installed to /usr/local/lib/irssi/modules by default (at least it got there for me), but that's changeable in the configure step, which my make script took care of already, so I simply moved the files:

sudo mv /usr/local/lib/irssi/modules/libpython.* /usr/lib/irssi/modules

Then load it in Irssi,

/load python
/py exec print "Hello World!"

Thanks, vmiklos. I really deserve no credit for getting this to build at all - I simply took his FrugalBuild script and translated it to a probably Gentoo-specific shell script.