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 compatible with Cassandra 0.7 and 0.8.
pycassa is open source under the MIT license.
Documentation can be found here:
http://pycassa.github.com/pycassa/
It includes installation instructions, a tutorial, API documentation, and a change log.
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
If easy_install is available, you can install the lastest pycassa release with:
easy_install pycassa
If you want to install from a source checkout, make sure you have Thrift installed, and run setup.py as a superuser:
easy_install thrift
python setup.py install
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):
...
cassandra.ttypes.NotFoundException: NotFoundException()
See the tutorial for more details.