A Primer on Scientific Programming With Python by Jans Pette Langtangen

A Primer on Scientific Programming With Python by Jans Pette Langtangen is the standard introductory text for the field. The second edition was published in 2009 and apparently contains important updates for the newer versions of Python. Langtangen's follow up book is Python Scripting for Computational Science (2010). He also has several scary-sounding books on "computational differential equations"