Programming Python, 4th Edition

Chapter 17. Databases and Persistence

“Give Me an Order of Persistence, but Hold the Pickles”

So far in this book, we’ve used Python in the system programming, GUI development, and Internet scripting domains—three of Python’s most common applications, and representative of its use as an application programming language at large. In the next four chapters, we’re going to take a quick look at other major Python programming topics: persistent data, data structure techniques, text and language processing, and Python/C integration.

These four topics are not really application areas themselves, but they are techniques that span domains. The database topics in this chapter, for instance, can be applied on the Web, in desktop GUI applications, and so on. Text processing is a similarly general tool. Moreover, none of these final four topics is covered exhaustively (each could easily fill a book alone), but we’ll sample Python in action in these domains and highlight their core concepts and tools. If any of these chapters spark your interest, additional resources are readily available in the Python world.

Persistence Options in Python

In this chapter, our focus is on persistent data—the kind that outlives a program that creates it. That’s not true by default for objects a script constructs, of course; things like lists, dictionaries, and even class instance objects live in your computer’s memory and are lost as soon as the script ends. To make data live longer, we need to ...