Howto install eric (Python IDE) on current Debian
 

If starting an installed 'eric' (4.3.x) from command line only gives you an
...
you don't need to fiddle around with different versions of eric and eric-api-files: all combinations (between_4.1.5-2_ and _4.3.7.1-1_) will fail, and bug report 532772 may be somewhat confusing.

Indeed you have to install their latest version from debian experimental this way:

This brings you libqscintilla2-5 2.3.2-1.1 and python-qscintilla2 2.3.2-1.1, which currently are reported to be in 'testing'. Together with the latest eric and eric-api-files (both 4.3.7.1-1) it works.

The funny thing about this (and the reason to post that): I had installed (and purged before) just this combination umpteen times before using synaptic without errors, but 'eric' constantly refused as shown above!

Maybe some apt guru has an explanation for this. The rest of us is just glad to have it fixed.

It doesn't make sense to me either. I'm hoping for someone who knows to post here as well. Logically, Synaptic is a front end GUI for apt. Therefore if synaptic will give you the install but apt won't I can't explain it. An they both use dpkg in their back end, so what's going on?

After an upgrade to KDE 4.4.3 (from debian/unstable now) yesterday I had to repeat the
apt-get install -t experimental libqscintilla2-5 python-qscintilla2
Yet don't exactly know why, but it worked again ,-)