[Tutor] When are strings interned?

[Angus Rodgers]

Hello, world!

This is my first post to the Tutor list (although I've already
posted to comp.lang.python a couple of times).

I'm currently reading Chapter 4 of Wesley Chun's book, "Core 
Python Programming" (2nd ed.).

I find this, in Python 2.5.4, on my Win98SE system (using IDLE):

>>> n = "colourless"
>>> o = "colourless"
>>> n == o
True
>>> n is o
True
>>> p = "green ideas"
>>> q = "green ideas"
>>> p == q
True
>>> p is q
False

Why the difference?
-- 
Angus Rodgers