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A simple SQLite3 store for Python objects

Project description

minidb is a Python module that utilizes the SQLite3 database library in order to store and retrieve Python objects. It utilizes Python’s __slots__ mechanism to determine the column names, and uses the class name for table names. Data is always stored as text in the database, but will be converted using the type specified in __slots__ (which therefore has to be a dict).

A very basic example

let’s define a “Person” object having an ID (that’s not a requirement, but we use it for good measure) and a name:

>>> class Person(object):
>>>    __slots__ = {'id': int, 'name': str}

The minidb.Store class represents our database. By default, it uses an in-memory database, but you can pass a filename to its constructor to persist the data to a file:

>>> import minidb
>>> db = minidb.Store('persons.db')

We can now simply create a person object and store it in the database (note that you can write an __init__ method, but you don’t have to, and it won’t be used by minidb when retrieving data from the database):

>>> john = Person()
>>> john.id = 42
>>> john.name = "John"
>>> db.save(john)

You should commit and close the DB after using it:

>>> db.commit()
>>> db.close()

Let’s have a look at the “persons.db” file with the “sqlite3” command-line utility and inspect what minidb has created:

sqlite> .schema CREATE TABLE Person (id TEXT, name TEXT);

Looks good (as already mentioned, the data type in the table will always be TEXT, and minidb takes care of converting the data during load/save). And this is the data that’s currently stored in the database:

sqlite> SELECT * FROM Person; 42|John

Loading data works similarly. Let’s start fresh (assuming the “Person” class will be defined as above) and load the stored Person:

>>> db = minidb.Store('persons.db')
>>> db.load(person)
[<__main__.Person object at 0x7fa17a52d210>]
>>> [(p.id, p.name) for p in db.load(Person)]
[(42, 'John')]

You can have a look at the API documentation using the “pydoc” command line utility or “help” in the interactive shell:

>>> help(minidb.Store)

See the file “minidb.py” for some examples on what you can do with minidb.

Remarks

The initial idea code for this project was code-named “ORM wie eine Kirchenmaus” and released on 2009-11-29.

– Thomas Perl <m@thp.io>; 2010-10-30

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