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Python SDK

The Python SDK allows developers to interact with the Casper Node using Python 3.9+. This page covers various examples of using this SDK.

Installation​

Before installing the library, you need to install dependencies from requirements.txt, which you can perform by running the following command:


    pip install -r requirements.txt

Finally, to install the library, run:


    pip install pycspr

Tests​

You can find examples of testing this library with python scripts in the test directory. To run the tests, we recommend the pytest library:

    pytest ./tests

Usage Examples​

In this section, we outline a couple of essential tasks you can accomplish with the Python SDK:

For further examples, take a look at the How-tos.

Sending a transfer​

This example shows you how to define and transfer funds between purses on a Casper network. Replace the path_to_cp2_account_key in the code below with the receiver's account public key.

    import os
    import pathlib
    import random
    import typing

    import pycspr
    from pycspr.client import NodeClient
    from pycspr.client import NodeConnectionInfo
    from pycspr.crypto import KeyAlgorithm
    from pycspr.types import PrivateKey
    from pycspr.types import Deploy
    from pycspr.types import PublicKey

    # path to cp1 secret key - defaults to NCTL user 1.
    path_to_cp1_secret_key = pathlib.Path(os.getenv("NCTL")) / "assets" / "net-1" / "users" / "user-1" / "secret_key.pem"

    # type of cp1 secret key - defaults to ED25519.
    type_of_cp1_secret_key = KeyAlgorithm.ED25519.name,

    # path to cp2 account key - defaults to NCTL user 2.
    path_to_cp2_account_key = pathlib.Path(os.getenv("NCTL")) / "assets" / "net-1" / "users" / "user-2" / "public_key_hex"

    # name of target chain - defaults to NCTL chain.
    chain_name = "casper-net-1"

    # host address of target node - defaults to NCTL node 1.
    node_host = "localhost"

    # Node API JSON-RPC port - defaults to 11101 @ NCTL node 1.
    node_port_rpc = 11101

    def _main(node_host, node_port_rpc, path_to_cp1_secret_key, type_of_cp1_secret_key,path_to_cp2_account_key, chain_name):
        """Main entry point.
        :param args: Parsed command line arguments.
        """
        # Set node client.
        client = _get_client(node_host, node_port_rpc)

        # Set counter-parties.
        cp1, cp2 = _get_counter_parties(path_to_cp1_secret_key, type_of_cp1_secret_key,path_to_cp2_account_key)

        # Set deploy.
        deploy: Deploy = _get_deploy(chain_name, cp1, cp2)

        # Approve deploy.
        deploy.approve(cp1)

        # Dispatch deploy to a node.
        client.deploys.send(deploy)

        #If deploy is successful send the indication
        print(f"Deploy dispatched to node [{node_host}]: {deploy.hash.hex()}")


    def _get_client(node_host, node_port_rpc) -> NodeClient:
        """Returns a pycspr client instance.
        """
        return NodeClient(NodeConnectionInfo(
            host=node_host,
            port_rpc=node_port_rpc,
        ))


    def _get_counter_parties(path_to_cp1_secret_key, type_of_cp1_secret_key,path_to_cp2_account_key) -> typing.Tuple[PrivateKey, PublicKey]:
        """Returns the 2 counter-parties participating in the transfer.
        """
        cp1 = pycspr.parse_private_key(
            path_to_cp1_secret_key,
            type_of_cp1_secret_key,
            )
        cp2 = pycspr.parse_public_key(
            path_to_cp2_account_key
            )

        return cp1, cp2


    def _get_deploy(chain_name, cp1: PrivateKey, cp2: PublicKey) -> Deploy:
        """Returns transfer deploy to be dispatched to a node.
        """
        # Set standard deploy parameters.
        deploy_params = pycspr.create_deploy_parameters(
            account = cp1,
            chain_name = chain_name
            )

        # Set deploy.
        deploy = pycspr.create_native_transfer(
            params = deploy_params,
            amount = int(2.5e9),
            target = cp2.account_hash,
            correlation_id = random.randint(1, 1e6)
            )

        return deploy


    # Entry point.
    if __name__ == '__main__':
        _main(node_host, node_port_rpc, path_to_cp1_secret_key, type_of_cp1_secret_key, path_to_cp2_account_key, chain_name)

Staking​

This example shows you how to define and stake funds with a validator.


    import os
    import pathlib

    import pycspr
    from pycspr.client import NodeClient
    from pycspr.client import NodeConnectionInfo
    from pycspr.crypto import KeyAlgorithm
    from pycspr.types import Deploy
    from pycspr.types import PrivateKey

    # path to cp1 secret key - defaults to NCTL user 1.
    path_to_validator_secret_key = pathlib.Path(os.getenv("NCTL")) / "assets" / "net-1" / "users" / "user-1" / "secret_key.pem"

    # type of cp1 secret key - defaults to ED25519.
    type_of_validator_secret_key = KeyAlgorithm.ED25519.name

    # path to session code wasm binary - defaults to NCTL bin/eco/add_bid.wasm.
    path_to_wasm = pathlib.Path(os.getenv("NCTL")) / "assets" / "net-1" / "bin" / "auction" / "add_bid.wasm"

    # amount to stake, i.e. bond, into the network.
    amount = int(2.5e9)

    # amount to charge delegators for service provision.
    delegation_rate = 2

    # name of target chain - defaults to NCTL chain.
    chain_name = "casper-net-1"

    # host address of target node - defaults to NCTL node 1.
    node_host = "localhost"

    # Node API JSON-RPC port - defaults to 11101 @ NCTL node 1.
    node_port_rpc = 11101

    def _main(node_host, node_port_rpc, path_to_validator_secret_key, type_of_validator_secret_key, chain_name, amount, delegation_rate, path_to_wasm):
        """Main entry point.
        :param args: Parsed command line arguments.
        """
        # Set node client.
        client: NodeClient = _get_client(node_host, node_port_rpc)

        # Set validator key.
        validator: PrivateKey = pycspr.parse_private_key(
            path_to_validator_secret_key,
            type_of_validator_secret_key,
            )

        # Set deploy.
        deploy: Deploy = _get_deploy(validator, chain_name, amount, delegation_rate, path_to_wasm)

        # Approve deploy.
        deploy.approve(validator)

        # Dispatch deploy to a node.
        client.deploys.send(deploy)

        print(f"Deploy dispatched to node [{node_host}]: {deploy.hash.hex()}")


    def _get_client(node_host, node_port_rpc) -> NodeClient:
        """Returns a pycspr client instance.
        """
        return NodeClient(NodeConnectionInfo(
            host = node_host,
            port_rpc = node_port_rpc,
        ))


    def _get_deploy(validator: PrivateKey, chain_name, amount, delegation_rate, path_to_wasm) -> Deploy:
        """Returns delegation deploy to be dispatched to a node.
        """
        # Set standard deploy parameters.
        deploy_params = pycspr.create_deploy_parameters(
            account = validator,
            chain_name = chain_name
            )

        # Set deploy.
        deploy = pycspr.create_validator_auction_bid(
            params = deploy_params,
            amount = amount,
            delegation_rate = delegation_rate,
            public_key = validator.as_public_key(),
            path_to_wasm = path_to_wasm
            )

        return deploy


    # Entry point.
    if __name__ == '__main__':
        _main(node_host, node_port_rpc, path_to_validator_secret_key, type_of_validator_secret_key, chain_name, amount, delegation_rate, path_to_wasm)

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