I second the vote for Eclipse with PyDev.
And.. (at least on Windows) I use Boa Constructor to build GUI front-ends.
If only the Boa gui builder was integrated into PyDev...wow!
As of 10-13-2015 Eclipse requires MacOSX 10.5 or greater. Eclipse is no longer a solution for those still on 10.4.11, with a venerable PPC (like myself and my very happy G5 G4 G3 that may run another 20 years).
The choices are becoming slim with PPC and 10.4.11.
I'm leaning toward jedit
jedit requires the Java Runtime Engine be installed. JRE 7 and higher requires an intel and 10.7.3 Lion
JRE 6 requires 10.6 (and 10.6 requires intel)
So, if using 10.4.11 you need Java for 10.4 from Apple, here:
https://support.apple.com/downloads/Java_for_Mac_OS_X_10_5_Update_4
And yet... this link's installer informed me that I already have a later version of java installed . I've never directly installed JRE, that I know of, unless it was through Software Update. So there is some misinformation somewhere, something I hate to spread (and so this disclaimer).
Here is the jedit compatibility page:
http://www.jedit.org/index.php?page=compatibility
My G5 and 10.4.11 requires jedit v4.3.3, according to the jedit install page, for compatibility. Assuming that page is accurate, I went here for 4.3.3 .dmg and .pdf manual.
http://sourceforge.net/projects/jedit/files/jedit/4.3.3/
It works with python code after loading a few plug-ins with the plug-in manager. I am not a pro coder, and at this time, jedit is more comprehensive than my needs, but I'm plowing through the manual. It does give me some desired feature.
The list of IDE's that will not run on 10.4.11 PPC is growing... however...
also trying the older TextMate 1.5.10 available here:
http://macromates.com/download
The TextMate 1.5.10 works, and can be used as simply as desired, but... it crashed my Firefox (latest version for PPC and 10.4.11) when going to the license key page for the 49 EUR purchase. Not a good sign. And per TOP, it is not free.
www.ninja-ide.org is only available as source for Mac. I'd rather not tweak it just so it will compile on 10.4.11 with a PPC.
If there are any other other suggestions for a simple, free, PPC MacOSX 10.4.11 python 3 IDE, with the simplicity of IDLE, but with line numbers and a little more capability, please post.
Thank you.