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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 compatible with Cassandra 0.7 and 0.8.

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:

Mailing List:

Installation

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 thrift
python setup.py install

Connecting

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.ConnectionPool('Keyspace1') # Defaults to connecting to the server at 'localhost:9160'
>>> pool = pycassa.ConnectionPool('Keyspace1', server_list=['192.168.2.10'])

See the tutorial for more details.

Basic Usage

To use the standard interface, create a ColumnFamily instance.

>>> pool = pycassa.ConnectionPool('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()
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