py-smoldot-light

Python bindings for the smoldot_light Rust crate using PyO3. The goal is to run a lightweight Polkadot client in Python and connect it to py-polkadot-sdk.

Overview

• Rust core: smoldot_light provides the light client implementation.
• Python API: SmoldotClient exposes JSON-RPC request/response plumbing.
• Build system: maturin builds and installs the extension module.

Quick Start

Build and install into your active virtualenv:

maturin develop

Example Usage (Python)

from smoldot_light import SmoldotClient

client = SmoldotClient()

# Load a chain spec JSON string (Polkadot, Kusama, or a local chain).
with open("polkadot.json", "r", encoding="utf-8") as f:
    chain_spec = f.read()

relay_chain_id = client.add_chain(chain_spec)

# If you are connecting a parachain, pass the relay chain id(s).
# asset_hub_id = client.add_chain(asset_hub_spec, relay_chain_ids=[relay_chain_id])

# Send a JSON-RPC request.
client.json_rpc_request(relay_chain_id, '{"id":1,"jsonrpc":"2.0","method":"system_name","params":[]}')

# Drain any available responses (non-blocking).
responses = client.drain_responses(relay_chain_id, max=10)
for msg in responses:
    print(msg)

Getting a Substrate Chain Spec

You can fetch a live Substrate chain spec JSON from a running node:

from substrateinterface import SubstrateInterface

substrate = SubstrateInterface(
    url="ws://127.0.0.1:9944"
)

response = substrate.rpc_request(method="sync_state_genSyncSpec", params=[False])

Notes

• JSON-RPC requests are queued; responses are drained via drain_responses.
• Chain specs are standard Substrate JSON spec files.