Adding a dict based interface to the python leveldb api

In the last post I showed how to install the python LevelDB bindings. Here is how to wrap the python LevelDB API into a dict like API with the help of UserDict.DictMixin. In a subclass we will extend the the simple key<string>:value<string> mapping to a dict with arbitrary JSON serializablie values.

from UserDict import DictMixin
import leveldb
import json

class LevelDict(DictMixin):
"""Dict Wrapper around the Google LevelDB Database"""
def init(self, path):
"""Constructor for LevelDict"""
self.path = path
self.db = leveldb.LevelDB(self.path)
def __getitem__(self, key):
    return self.db.Get(key)

def __setitem__(self, key, value):
    self.db.Put(key, value)

def __delitem__(self, key):
    self.db.Delete(key)

def __iter__(self):
    for k, v in self.db.RangeIter():
        yield v

def keys(self):
    return [k for k, v in self.db.RangeIter()]

def iteritems(self):
    return self.db.RangeIter()

def rangescan(self, start=None, end=None):
    if start is None and end is None:
        return self.db.RangeIter()
    elif end is None:
        return self.db.RangeIter(start)
    else:
        return self.db.RangeIter(start, end)

To store more than just strings we will add JSON serialization to a subclass:

class LevelJsonDict(LevelDict):
    """Dict Wrapper around the Google LevelDB Database with JSON serialization"""
    def __getitem__(self, key):
        return json.loads(LevelDict.__getitem__(self, key))

    def __setitem__(self, key, value):
        LevelDict.__setitem__(self, key, json.dumps(value))

    def iteritems(self):
        for k, v in LevelDict.iteritems(self):
            yield k, json.loads(v)

    def rangescan(self, start=None, end=None):
        for k, v in LevelDict.rangescan(self, start, end):
            yield k, json.loads(v)

Now you have a fast JSON Store with a Dict based Interface and a LevelDB backend.