kad.py
Python3 implementation of the Kademlia DHT data store.
Useful for distributing a key-value store in a decentralized manner.
To create a new DHT swarm, just call DHT() with the host and port that you will listen on. To join an existing DHT swarm, also provide bootstrap host and port numbers of any existing node. The nodes will discover the rest of the swarm as appropriate during usage.
Example: A two-node DHT
from kad import DHT
host1, port1 = 'localhost', 3000
dht1 = DHT(host1, port1)
host2, port2 = 'localhost', 3001
dht2 = DHT(host2, port2, seeds=[(host1, port1)])
dht1["my_key"] = [u"My", u"json-serializable", u"Object"]
print (dht2["my_key"]) # blocking get
dht2.get ("my_key", lambda data: print (data)) # threaded getExample: Persistent storage
We can use a custom storage for local data. Storage parameter must an object with getitem and setitem. In this example we use shelve to create a persistent storage.
from kad import DHT
import shelve
host, port = 'localhost', 3000
dht = DHT(host, port, storage=shelve.open ('sto.dat'))Example: Custom hash function
By default, kad.py hash the keys with md5 function. We can provide a custom hash_function. Note: Keep in mind that hash functions must return int values for this implementation.
from kad import DHT
host, port = 'localhost', 3000
dht = DHT(host, port, hash_function=lambda key: int(hashlib.sha256(key.encode('utf8')).hexdigest(), 16))Example: Custom request handler
You can extend the default DHTRequestHandler to intercept any kind of messages.
from kad import *
class CustomRequestHandler (kad.DHTRequestHandler):
def handle_store(self, message):
print (message['value'])
return super (CustomRequestHandler, self).handle_store (message)
d = DHT ('localhost', 3030, requesthandler=CustomRequestHandler)
d['ciao'] = {'hola': 12}Example: Iterate over DHT keys
You can use the DHT object as iterator for stored keys.
from kad import DHT
d = DHT ('localhost', 3100)
d['ciao'] = 'mondo'
d['hello'] = 'world'
for key in d:
print (key, d[key])
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