If you are using Cassandra 0.6, get pycassa 0.3.0 from the Downloads section and read the documentation contained within. This README applies to the current state of pycassa, which tracks Cassandra 0.7.
See the wiki for more compatibility notes.
pycassa is a python client library for Apache Cassandra with the following features:
- Auto-failover for normal or thread-local connections
- Connection pooling
- A batch interface
- A method to map an existing class to a Cassandra column family
Documentation can be found here:
http://pycassa.github.com/pycassa/
It includes installation instructions, a tutorial, API documentation, and a change log.
IRC:
- Use channel #cassandra 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 use:
easy_install pycassa
The simplest way to install manually is to copy the pycassa directories to your program. If you want to install, make sure you have thrift installed, and run setup.py as a superuser.
easy_install thrift05
python setup.py install
All functions are documented with docstrings. To read usage documentation, you can use help:
>>> import pycassa
>>> help(pycassa.ColumnFamily.get)
To get a connection pool, pass a Keyspace and an optional list of servers:
>>> pool = pycassa.connect('Keyspace1') # Defaults to connecting to the server at 'localhost:9160'
>>> pool = pycassa.connect('Keyspace1', ['192.168.2.10:9160'])
See the tutorial for more details.
To use the standard interface, create a ColumnFamily instance.
>>> pool = pycassa.connect('Keyspace1')
>>> cf = pycassa.ColumnFamily(pool, 'Standard1')
>>> cf.insert('foo', {'column1': 'val1'})
1261349837816957
>>> cf.get('foo')
{'column1': 'val1'}
insert() also acts to update values:
>>> cf.insert('foo', {'column1': 'val2'})
1261349910511572
>>> cf.get('foo')
{'column1': 'val2'}
You may insert multiple columns at once:
>>> cf.insert('bar', {'column1': 'val3', 'column2': 'val4'})
1261350013606860
>>> cf.multiget(['foo', 'bar'])
{'foo': {'column1': 'val2'}, 'bar': {'column1': 'val3', 'column2': 'val4'}}
>>> cf.get_count('bar')
2
get_range() returns an iterable. Call it with 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'])
1261350220106863
>>> cf.get('bar')
{'column2': 'val4'}
>>> cf.remove('bar')
1261350226926859
>>> cf.get('bar')
Traceback (most recent call last):
...
cassandra.ttypes.NotFoundException: NotFoundException()