Programming Python, 3rd Edition

19.1. "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 domainsthree of Python's most common applications, and representative o...

19.2. Persistence Options in Python In this chapter, our focus is on persistent datathe kind that outlives a program that creates it. That's not true by default for objects a script constructs; things like lists, dictionaries, and even class insta...

19.3. DBM Files Flat files are handy for simple persistence tasks, but they are generally geared toward a sequential processing mode. Although it is possible to jump around to arbitrary locations with seek calls, flat files don't provide much...

19.4. Pickled Objects Probably the biggest limitation of DBM keyed files is in what they can store: data stored under a key must be a simple text string. If you want to store Python objects in a DBM file, you can...

19.5. Shelve Files Pickling allows you to store arbitrary objects on files and file-like objects, but it's still a fairly unstructured medium; it doesn't directly support easy access to members of collections of pickled objects. H...

19.6. The ZODB Object-Oriented Database ZODB, the Zope Object Database, is a full-featured and Python-specific object-oriented database system. ZODB can be thought of as a more powerful alternative to Python's shelves. It allows you to store nearl...

19.7. SQL Database Interfaces The shelve module and ZODB package of the prior sections are powerful tools. Both allow scripts to throw nearly arbitrary Python objects on a keyed-access file and load them back laterin a single step for shel...

19.8. PyForm: A Persistent Object Viewer Instead of going into additional database interface details that are freely available at Python.org, I'm going to close out this chapter by showing you one way to combine the GUI technology we met earl...