Eric is a full featured Python and Ruby editor and IDE, written
in python. It is based on the cross platform Qt gui toolkit, integrating
the highly flexible Scintilla editor control. It is designed to be
usable as everdays' quick and dirty editor as well as being usable as a
professional project management tool integrating many advanced features
Python offers the professional coder.

Current stable version is eric4 based on Qt4. For Qt3 based systems
eric3 is still available.

Pycha is a very simple Python package for drawing charts using the great Cairo library. Its goals are:

• Lightweight
  
• Simple to use
  
• Nice looking with default values
  
• Customization
  

It won't try to draw any possible chart on earth but draw the most common ones nicely. There are some other options you may want to look at like pyCairoChart

Pycha is based on Plotr which is based on PlotKit. Both libraries are written in JavaScript and are great for client web programming. I needed the same for the server side so that's the reason I ported Plotr to Python. Now we can deliver charts to people with JavaScript disabled or embed them in PDF reports.

StatPy:
Statistical Computing with Python

Welcome to StatPy, a collection of resources to help you do
statistical computing with Python, with a special emphasis on astrostatistics
(statistics in astronomy). This web site is brand-spanking-new, and still very
much under construction; please be patient with our "dust" and check back
again frequently as building continues.

What idioms should I use to make my code easier to read?

Read "The Python Cookbook", especially the first few chapters.
It's a great source of well-written Python code examples.