in-memory database in Python

Question

I'm doing some queries in Python on a large database to get some stats out of the database. I want these stats to be in-memory so other programs can use them without going to a database.

I was thinking of how to structure them, and after trying to set up some complicated nested dictionaries, I realized that a good representation would be an SQL table. I don't want to store the data back into the persistent database, though. Are there any in-memory implementations of an SQL database that supports querying the data with SQL syntax?

Answer 1

SQLite3 might work. The Python interface does support the in-memory implementation that the SQLite3 C API offers.

From the spec:

You can also supply the special name :memory: to create a database in RAM.

It's also relatively cheap with transactions, depending on what you are doing. To get going, just:

import sqlite3
conn = sqlite3.connect(':memory:')

You can then proceed like you were using a regular database.

Depending on your data - if you can get by with key/value (strings, hashes, lists, sets, sorted sets, etc) - Redis might be another option to explore (as you mentioned that you wanted to share with other programs).

Answer 2

I guess, SQLite3 will be the best option then.

If possible, take a look at memcached. (for key-value pair, lighting fast!)

UPDATE 1:

HSQLDB for SQL Like tables. (no python support)

Answer 3

You could possibly use a database like SQLite. It's not strictly speaking in memory, but it is fairly light and would be completely separate from your main database.