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Programming Python, 3rd Edition
book

Programming Python, 3rd Edition

by Mark Lutz
August 2006
Intermediate to advanced content levelIntermediate to advanced
1600 pages
51h 46m
English
O'Reilly Media, Inc.
Content preview from Programming Python, 3rd Edition

Step 2: Storing Records Persistently

So far, we’ve settled on a dictionary-based representation for our database of records, and we’ve reviewed some Python data structure concepts along the way. As mentioned, though, the objects we’ve seen so far are temporary—they live in memory and they go away as soon as we exit Python or the Python program that created them. To make our people persistent, they need to be stored in a file of some sort.

Using Formatted Files

One way to keep our data around between program runs is to write all the data out to a simple text file, in a formatted way. Provided the saving and loading tools agree on the format selected, we’re free to use any custom scheme we like.

Test data script

So that we don’t have to keep working interactively, let’s first write a script that initializes the data we are going to store (if you’ve done any Python work in the past, you know that the interactive prompt tends to become tedious once you leave the realm of simple one-liners). Example 2-1 creates the sort of records and database dictionary we’ve been working with so far, but because it is a module, we can import it repeatedly without having to retype the code each time. In a sense, this module is a database itself, but its program code format doesn’t support automatic or end-user updates as is.

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Publisher Resources

ISBN: 0596009259Supplemental ContentErrata Page