dump_cassandra.py

import json
from pycassa.pool import ConnectionPool
from pycassa.columnfamily import ColumnFamily
from pycassa.cassandra.ttypes import ConsistencyLevel, NotFoundException

HOSTS = ['localhost']

pool = ConnectionPool('my_keyspace', HOSTS)
my_cf = ColumnFamily(pool, 'my_cf')

for row in my_cf.get_range():
    output = { 'KEY': row[0] }
    for column, value in row[1].iteritems():
        output[column] = value

    print json.dumps(output)