pycassa

pycassa is a python client library for Apache Cassandra with the following features:

• Automatic failover and operation retries
• Connection pooling
• Multithreading support
• A batch interface
• A class for mapping classes to Cassandra column families

The latest release is fully compatible with Cassandra 0.8 and 1.0, and compatible with the data API of 0.7.

pycassa is open source under the MIT license.

Documentation

Documentation can be found here:

http://pycassa.github.com/pycassa/

It includes installation instructions, a tutorial, API documentation, and a change log.

Getting Help

IRC:

• Use the #cassandra channel on irc.freenode.net. If you don't have an IRC client, you can use freenode's web based client.

Mailing List:

• User list: http://groups.google.com/group/pycassa-discuss
• Developer list: http://groups.google.com/group/pycassa-devel

Installation

If pip is available, you can install the lastest pycassa release with:

pip install pycassa

If you want to install from a source checkout, make sure you have Thrift installed, and run setup.py as a superuser:

pip install thrift
python setup.py install

Basic Usage

To get a connection pool, pass a Keyspace and an optional list of servers:

>>> import pycassa
>>> pool = pycassa.ConnectionPool('Keyspace1') # Defaults to connecting to the server at 'localhost:9160'
>>>
>>> # or, we can specify our servers:
>>> pool = pycassa.ConnectionPool('Keyspace1', server_list=['192.168.2.10'])

To use the standard interface, create a ColumnFamily instance.

>>> pool = pycassa.ConnectionPool('Keyspace1')
>>> cf = pycassa.ColumnFamily(pool, 'Standard1')
>>> cf.insert('foo', {'column1': 'val1'})
>>> cf.get('foo')
{'column1': 'val1'}

insert() will also update existing columns:

>>> cf.insert('foo', {'column1': 'val2'})
>>> cf.get('foo')
{'column1': 'val2'}

You may insert multiple columns at once:

>>> cf.insert('bar', {'column1': 'val3', 'column2': 'val4'})
>>> cf.multiget(['foo', 'bar'])
{'foo': {'column1': 'val2'}, 'bar': {'column1': 'val3', 'column2': 'val4'}}
>>> cf.get_count('bar')
2

get_range() returns an iterable. You can use list() to convert it to a list:

>>> list(cf.get_range())
[('bar', {'column1': 'val3', 'column2': 'val4'}), ('foo', {'column1': 'val2'})]
>>> list(cf.get_range(row_count=1))
[('bar', {'column1': 'val3', 'column2': 'val4'})]

You can remove entire keys or just a certain column:

>>> cf.remove('bar', columns=['column1'])
>>> cf.get('bar')
{'column2': 'val4'}
>>> cf.remove('bar')
>>> cf.get('bar')
Traceback (most recent call last):
...
pycassa.NotFoundException: NotFoundException()

See the tutorial for more details.