Prior to building irssi-python, you'll need Python 2.4, glib 2.0, and Irssi 
installed.

1. Download and unpack the irssi source (ie irssi-0.8.10a.tar.gz) if you haven't
   done so already. irssi-python will need access to Irssi's headers. 

2. Run the configure script, making sure to specify the correct location of
   Irssi's distribution with the --with-irssi switch. For example:

   $ configure --with-irssi=~/irssi-0.8.10

   If configure has trouble linking a Python test program due to missing pthread
   symbols (occasionally on FreeBSD), try:

   $ LDFLAGS="-pthread" configure --with-irssi=<path/to/distro>

   Make sure the prefix for irssi-python matches Irssi's (/usr, /usr/local,
   etc) so that the module and scripts are installed in the right places. 

3. As usual, run make.

4. make install if OK. libpython.so should be copied to irssi/modules/,
   scripts to irssi/scripts/ and irssi-python.html to doc/irssi/.
  
5. You should be able to load the module in Irssi after installing, IE:
   
   /load python

   If you get missing pthread symbols, you may have to preload the thread safe
   C library before running irssi. export LD_PRELOAD=/usr/lib/libc_r.so seems to
   work on FreeBSD.

   You may want to load one of the example scripts like hello or fork.

Also check out README and docs/irssi-python.html