Reference books

Python

• Official Python 3 Tutorial

Databases

• Concise Guide to Databases: A Practical Introduction
• Big Data: Principles and best practices of scalable realtime data systems
• Introduction to SQL: Mastering the Relational Database Language
• MySQL
• Learning SQL
• NoSQL distilled
• NoSQL For Dummies

Data formats

• Beginning JSON
• Beginning XML
• XML in a Nutshell
• RESTful Web Services