IOn Sat, Dec 12, 2015 at 6:31 PM, Frank Millman <fr...@chagford.com> wrote: > I have found a workaround for my problem, but first I needed to understand > what was going on more clearly. This is what I have figured out. > > 1. The solution in the SO article is a bit of sleight of hand, though very > effective. It does not create a Decimal type in sqlite3. It simply provides > a way of converting Decimal objects to strings when you pass them into the > database, and converting them back to Decimal types when you read them back. > > 2. This works if you only use sqlite3 as a storage mechanism, and use Python > to perform any arithmetic required. It fails when you try to use sqlite3 to > perform arithmetic, as it uses floating point internally and suffers from > the same problem that Python does when trying to mix floating point and > precise decimal representation.
There's another possibility, and that's fixed-point arithmetic. You store the numbers as integers - probably cents, if you're talking about dollar amounts - and as long as the scaled values fit inside the available integer type (probably 64-bit), you'll be fine. Or, of course, you could switch to a database back end that actually supports NUMERIC data. ChrisA -- https://mail.python.org/mailman/listinfo/python-list
