+1 for Wing Professional IDE.
The "Go To Definition" and "Source Assistant" can really go a long way to assist in your better python learning.
It has Vi and Emacs Emulation too, if U need either of them. Only the UI is bad, if on Windows (as it is based on GTK), It rocks on ubuntu.
If you are using any text editor, (Scite is my choice) then U'd do well by using ipyton console. (U can do a easy_install of ipython, if easy_install is installed)
With python itself providing debug options, and ipython and bash shell offering good auto-complete options, it is not really a that bad option to do away with any IDE. But if you still want an IDE (as I want), Wing Professional is the best one out there.
I have also tried SPE, PyDev and am not impressed enough to consider them; but indeed some features of PyDev like verifying whether a variable is used or not and auto-setting of different modes- Debug, PyDev, Java Browsing when U run and application is available in PyDev alone.
If U only need a good Syntax highlighting SciTE (on windows, SciTE based Notepad++) is a good option. If U need "project" option and auto-complete with Syntax highlighting, Komodo Edit is the best option. It also supports many other languages. If you want everything but the space shuttle (minus some special features of PyDev), Wing Professional is the best IDE currently available.
Most important thing is "Choose one and go with it"