patract-interface 0.1.0

Substrate Contract SDK for Python As a part of Himalia

Himalia PatractPy

Substrate Contract SDK for Python As a part of Himalia

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PatractPy is a contract SDK to support the development of Python scripts that interact with contracts, including automated scripts to support testing. Unlike PatractGo, PatractPy is mainly for script development, so PatractPy mainly completes contract-related RPC interfaces, and completes contract deployment and instantiation-related operations.

PatractPy will provide support for europa env, which is a good environment for contract exec sandbox, With PatractPy, we can write contract unittest by python, which is more friendly to developer and can easy use other test tools.

PatractPy will be based on polkascan's Python Substrate Interface, which is a Python sdk for Substrate.

Element Group for disscusion: https://app.element.io/#/room/#PatractLabsDev:matrix.org

PatractPy will achieve the following support:

• Some support that missing in polkascan's Python Substrate Interface, which is needed for contracts
• Provide Scanning and monitoring support for contract to do statistics and analysis
• Provide a SDK development example for ERC20 contract
• Support For unittest to canvas or europa env.

For Unittest, should install europa at first.

europa --version
europa 0.1.0-3f71403-x86_64-linux-gnu

All of test pased by europa environment.

Basic Apis For Contracts

As polkascan's Python Substrate Interface has provide some support to contract api, so we not need to important the api for contract calls, but there is some api to add:

• SubstrateSubscriber is a subscriber support to subscribe data changes in chain, for example, the events in chain.
• get_contract_event_type add event decode support for contracts.

ContractObserver

ContractObserver can observer events for a contract:

substrate=SubstrateInterface(url="ws://127.0.0.1:9944", type_registry_preset='canvas')
contract_metadata = ContractMetadata.create_from_file(
    metadata_file=os.path.join(os.path.dirname(__file__), 'constracts', 'ink', 'erc20.json'),
    substrate=substrate
)
observer = ContractObserver("0x8eaf04151687736326c9fea17e25fc5287613693c912909cb226aa4794f26a48", contract_metadata, substrate)

# for some handlers
observer.scanEvents()

The handler function can take the erc20 support as a example.

ERC20 API

ERC20 api provide a wapper to erc20 contract exec, read and observer events, it can be a example for contracts api calling.

# init api
substrate=SubstrateInterface(url="ws://127.0.0.1:9944", type_registry_preset='canvas')

contract_metadata = ContractMetadata.create_from_file(
    metadata_file=os.path.join(os.path.dirname(__file__), 'constracts', 'ink', 'erc20.json'),
    substrate=substrate
)

alice = Keypair.create_from_uri('//Alice')
bob = Keypair.create_from_uri('//Bob')

# erc20 api
erc20 = ERC20.create_from_contracts(
    substrate= substrate, 
    contract_file= os.path.join(os.path.dirname(__file__), 'constracts', 'ink', 'erc20.wasm'),
    metadata_file= os.path.join(os.path.dirname(__file__), 'constracts', 'ink', 'erc20.json')
)

# deplay a erc20 contract
erc20.putAndDeploy(alice, 1000000 * (10 ** 15))

# read total supply
total_supply = erc20.totalSupply()

# transfer
erc20.transferFrom(alice,
    fromAcc=alice.ss58_address, 
    toAcc=bob.ss58_address, 
    amt=10000)

erc20.transfer(alice, bob.ss58_address, 10000)

# get balance
alice_balance = erc20.balanceOf(alice.ss58_address)

# approve
erc20.approve(alice, spender=bob.ss58_address, amt=10000)

# get allowance
alice_allowance = erc20.allowance(alice.ss58_address, bob.ss58_address)

ERC20Observer is a event observer for erc20 contract:

observer = ERC20Observer.create_from_address(
    substrate = substrate, 
    contract_address = contract_address,
    metadata_file= os.path.join(os.path.dirname(__file__), 'constracts', 'ink', 'erc20.json')
)

def on_transfer(num, fromAcc, toAcc, amt):
    logging.info("on_transfer in block[{}] : {} {} {}".format(num, fromAcc, toAcc, amt))

def on_approval(num, owner, spender, amt):
    logging.info("on_approval in block[{}] : {} {} {}".format(num, owner, spender, amt))

observer.scanEvents(on_transfer = on_transfer, on_approval = on_approval)

Unittest Node Environment

PatractPy can support write contract unittest by node environment.

At First We need install europa.

from patractinterface.contracts.erc20 import ERC20
from patractinterface.unittest.env import SubstrateTestEnv

class UnittestEnvTest(unittest.TestCase):
    @classmethod
    def setUp(cls):
        # start env or use canvas for a 6s block
        cls.env = SubstrateTestEnv.create_europa(port=39944)
        cls.env.startNode()

        cls.api = SubstrateInterface(url=cls.env.url(), type_registry_preset=cls.env.typ())
        cls.alice = Keypair.create_from_uri('//Alice')
        cls.bob = Keypair.create_from_uri('//Bob')

        cls.erc20 = ERC20.create_from_contracts(
            substrate= cls.substrate, 
            contract_file= os.path.join(os.path.dirname(__file__), 'constracts', 'ink', 'erc20.wasm'),
            metadata_file= os.path.join(os.path.dirname(__file__), 'constracts', 'ink', 'erc20.json')
        )
        cls.erc20.putAndDeploy(alice, 1000000 * (10 ** 15))

        return

    def tearDown(cls):
        cls.env.stopNode()

    def test_transfer(self):
        self.erc20.transferFrom(alice,
            fromAcc=alice.ss58_address, 
            toAcc=bob.ss58_address, 
            amt=10000)
        # some more test case

if __name__ == '__main__':
    unittest.main()

By example, we can use python to write testcase for some complex logics, by europa, we can test the contracts for python scripts.