ocpp-codec - OCPP messages encoder-decoder

ocpp-codec provides dataclasses definitions of OCPP messages and types, in both version 1.6 and 2.0 of the protocol.

It also provides a JSON pre-serializer and post-deserializer to exchange messages (see below).

It does not provide an API to write an OCPP server or client.

Pre-serializer

Turn an OCPP message dataclass instance into a basic Python dict representing the JSON payload:

import datetime
import json

from ocpp_codec import serializer
from ocpp_codec import structure
from ocpp_codec.v20 import messages
from ocpp_codec.v20 import types

response_payload = messages.BootNotification.Response(
    datetime.datetime(2013, 2, 1, 20, 53, 32, 486000, datetime.timezone.utc),
    300,
    types.RegistrationStatusEnum.Accepted,
)
call_result = structure.CallResult("19223201", response_payload)
pre_serialized = serializer.serialize(call_result)

print(pre_serialized)
# [3, '19223201', {'currentTime': '2013-02-01T20:53:32.486000+00:00', 'interval': 300, 'status': 'Accepted'}]

print(json.dumps(pre_serialized))
# [3, "19223201", {"currentTime": "2013-02-01T20:53:32.486000+00:00", "interval": 300, "status": "Accepted"}]

As you can see in this example the pre-serialized data already converted datetime and enum.Enum fields to strings. The result can then directly be given to json.dumps to get the JSON string to be sent as an RPC.

Post-deserializer

Turn a Python dict (extracted from a JSON string) to an OCPP message dataclass:

import json

from ocpp_codec import compat
from ocpp_codec import serializer
from ocpp_codec.v20 import messages

deserialized = json.loads("""[3, "19223201", {"currentTime": "2013-02-01T20:53:32.486000+00:00", "interval": 300, "status": "Accepted"}]""")
call_result = serializer.parse(deserialized, 'BootNotification', protocol=compat.OcppJsonProtocol.v20)

print(call_result.uniqueId)
# 19223201

print(call_result.payload)
# BootNotification.Response(currentTime=datetime.datetime(2013, 2, 1, 20, 53, 32, 486000, tzinfo=tzutc()), interval=300, status=<RegistrationStatusEnum.Accepted: 'Accepted'>)

As you can see in this example, the post-deserialized payload is a dataclass holding python data types such as datetime and enum.Enum.

Implemented messages

You can find messages implemented for OCPP version 1.6 here and for OCPP version 2.0 here.