19 principles behind Python from Tim Peters: http://www.python.org/dev/culture.html
Of the 19, these 9 are my favorites:
Beautiful is better than ugly.
Explicit is better than implicit.
Simple is better than complex.
Complex is better than complicated.
Flat is better than nested.
There should be one — and preferably only one — obvious way to do it.
Now is better than never.
If the implementation is hard to explain, it’s a bad idea.
If the implementation is easy to explain, it may be a good idea.