Overview

Dobbin is a fast and convenient way to persist a Python object graph on disk.

The object graph consists of persistent nodes, which are objects that are based on one of the persistent base classes::

from dobbin.persistent import Persistent

foo = Persistent()
foo.bar = 'baz'

Each of these nodes can have arbitrary objects connected to it; the only requirement is that Python's pickle <http://docs.python.org/library/pickle.html>_ module can serialize the objects.

Persistent objects are fully object-oriented::

class Frobnitz(Persistent):
    ...

The object graph is built by object reference::

foo.frob = Frobnitz()

To commit changes to disk, we use the commit() method from the transaction <http://pypi.python.org/pypi/transaction>_ module. Note that we must first elect a root object, thus connecting the object graph to the database handle::

from dobbin.database import Database
import transaction

jar = Database('data.fs')
jar.elect(foo)

transaction.commit()

Consequently, if we want to make changes to one or more objects in the graph, we must first check out the objects in question::

from dobbin.persistent import checkout

checkout(foo)
foo.bar = 'boz'

transaction.commit()

The checkout(obj) function puts the object in shared state. It only works on object that are persistent nodes.

Dobbin is available on Python 2.6 and up including Python 3.x.

Key features:

• 100% Python, fully compliant with PEP8 <http://www.python.org/dev/peps/pep-0008/>_
• Threads share data when possible
• Multi-threaded, multi-process MVCC <http://en.wikipedia.org/wiki/Multiversion_concurrency_control>_ concurrency model
• Efficient storage and streaming of binary blobs
• Pluggable architecture

Getting the code

You can download <http://pypi.python.org/pypi/Dobbin#downloads>_ the package from the Python package index or install the latest release using setuptools or the newer distribute <http://packages.python.org/distribute/>_ (required for Python 3.x)::

$ easy_install dobbin

Note that this will install the transaction <http://pypi.python.org/pypi/transaction>_ module as a package dependency.

The project is hosted in a GitHub repository <http://github.com/malthe/dobbin>. Code contributions are welcome. The easiest way is to use the pull request <http://help.github.com/pull-requests/> interface.

Author and license

Written by Malthe Borch [email protected].

This software is made available under the BSD license.