Python jobs are a scarce commodity in Belgium.  If you are a Python dev looking for a job and you don’t want to end selling your soul to PHP or something, you can take a shot at one of these.

Big ones

BICS (Belgacom)

http://www.bics.com/ (LinkedIn) — Telecoms, 400+ employees, Bruxelles.
Pure python projects and a bit of Django.  Part of quite an old belgian telecom institution, so brace yourself and be ready to deal with whatever it entails in terms of technical environment.  Some of the Glassdoor’s reviews are quite interesting: some are excellent, others completely scary.

GDF Suez

http://www.gdfsuez.com/ (LinkedIn) — Energy.
Couldn’t find any actual job offers, but I’ve been contacted for Python projects there (without any other concrete information).  However, digging a bit can bring some elements, like Eric Gazoni’s LinkedIn profile (one of Adimian’s employees, see below), mentioning several Python jobs at GDF.

Middle-sized

Odoo (formerly OpenERP)

https://www.odoo.com/ (LinkedIn) — Software (ERP) development and edition, 100+ employees (in Belgium), Walloon Brabant.
Strong skills in JS will be much appreciated to understand and work on their web client.  You can have a look on what they’re doing on their Github repo.
Flip-flopping management and you’ll have to work with Indians.  But you’ll evolve among great colleagues.

CIRB (Centre d’Informatique pour la Région Bruxelloise)

http://www.cirb.be/ (LinkedIn) — Public sector, 201-500 employees*, Bruxelles.
Django projects for public sector.  One of their projects: Fix my street.  It’s pointless to contact them directly: they never answer.

Note that I have no idea how you are supposed to apply there.  They publish online offers but never answer when you contact them.  Apparently the only way to obtain an interview is to go through a recruitment or consultancy company, but everytime I got contacted for a job there it was to start within 3 to 5 days: it’s not even possible to go through the interview process in such a short time window, especially not with a consultancy company.
I don’t know who’s in charge of recruitment there, but it’s a textbook case of failure.  It’s a shame because their software solution has quite a nice reputation.

Smaller ones

Adimian

http://www.adimian.com/ (LinkedIn) — Software consultancy, 1-10 employees*, Walloon Brabant.

Code On

http://code-on.eu/ (LinkedIn) — Web agency, 1-10 employees*, East Flanders.
Django projects.

Mobile Vikings

https://mobilevikings.be/ (LinkedIn) — Telecoms, 51-200 employees*, Limburg.
Python, Django, Freeswitch based projects.

Cluepoints

http://www.cluepoints.com/ (LinkedIn) — Statistical monitoring, 15-25 employees, Walloon Brabant.
Pylons framework, SQLAlchemy, MySQL, MongoDB and ZMQ.

Intersentia

http://firstsoftware.be/ (LinkedIn) — Publishing, 11-50 employees*, Antwerp.
Most used technologies are Flask, SQLAlchemy, PyQt and Django.

* source: LinkedIn