frisitano / py-reef-interface

Python Reef Interface

Python Reef Interface

Python Reef Interface Library

Description

This library specializes in interfacing with the Reef node, providing additional convenience methods to deal with SCALE encoding/decoding (the default output and input format of the Substrate JSONRPC), metadata parsing, type registry management and versioning of types.

Documentation

Installation

pip install reef-interface

Initialization

The following examples show how to initialize:

from reefinterface import ReefInterface

reef = ReefInterface(url="testnet")

url can be testnet, mainnet or an ws://<url> URL for custom node.

Features

Retrieve extrinsics for a certain block

# Set block_hash to None for chain tip
block_hash = "0x51d15792ff3c5ee9c6b24ddccd95b377d5cccc759b8e76e5de9250cf58225087"

# Retrieve extrinsics in block
result = reef.get_block(block_hash=block_hash)

for extrinsic in result['extrinsics']:
    if extrinsic.address:
        signed_by_address = extrinsic.address.value
    else:
        signed_by_address = None

    print('\nPallet: {}\nCall: {}\nSigned by: {}'.format(
        extrinsic.call_module.name,
        extrinsic.call.name,
        signed_by_address
    ))

    # Loop through call params
    for param in extrinsic.params:

        if param['type'] == 'Compact<Balance>':
            param['value'] = '{} {}'.format(param['value'] / 10 **eef
            r.token_decimals, reef.token_symbol)

        print("Param '{}': {}".format(param['name'], param['value']))

Subscribe to new block headers

def subscription_handler(obj, update_nr, subscription_id):

    print(f"New block #{obj['header']['number']} produced by {obj['author']}")

    if update_nr > 10:
        return {'message': 'Subscription will cancel when a value is returned', 'updates_processed': update_nr}


result = reef.subscribe_block_headers(subscription_handler, include_author=True)

Storage queries

The modules and storage functions are provided in the metadata (see reef.get_metadata_storage_functions()), parameters will be automatically converted to SCALE-bytes (also including decoding of SS58 addresses).

Example:

result = reef.query(
    module='System',
    storage_function='Account',
    params=['F4xQKRUagnSGjFqafyhajLs94e7Vvzvr8ebwYJceKpr8R7T']
)

print(result.value['nonce'])
print(result.value['data']['free'])

Or get the account info at a specific block hash:

account_info = reef.query(
    module='System',
    storage_function='Account',
    params=['F4xQKRUagnSGjFqafyhajLs94e7Vvzvr8ebwYJceKpr8R7T'],
    block_hash='0x176e064454388fd78941a0bace38db424e71db9d5d5ed0272ead7003a02234fa'
)

print(account_info.value['nonce']) #  7673
print(account_info.value['data']['free']) # 637747267365404068

Storage subscriptions

When a callable is passed as kwarg subscription_handler, there will be a subscription created for given storage query. Updates will be pushed to the callable and will block execution until a final value is returned. This value will be returned as a result of the query and finally automatically unsubscribed from further updates.

def subscription_handler(account_info_obj, update_nr, subscription_id):

    if update_nr == 0:
        print('Initial account data:', account_info_obj.value)

    if update_nr > 0:
        # Do something with the update
        print('Account data changed:', account_info_obj.value)

    # The execution will block until an arbitrary value is returned, which will be the result of the `query`
    if update_nr > 5:
        return account_info_obj


result = reef.query("System", "Account", ["5GNJqTPyNqANBkUVMN1LPPrxXnFouWXoe2wNSmmEoLctxiZY"],
                         subscription_handler=subscription_handler)

print(result)

Query a mapped storage function

Mapped storage functions can be iterated over all key/value pairs, for these type of storage functions query_map can be used.

The result is a QueryMapResult object, which is an iterator:

# Retrieve the first 199 System.Account entries
result = reef.query_map('System', 'Account', max_results=199)

for account, account_info in result:
    print(f"Free balance of account '{account.value}': {account_info.value['data']['free']}")

These results are transparently retrieved in batches capped by the page_size kwarg, currently the maximum page_size restricted by the RPC node is 1000

# Retrieve all System.Account entries in batches of 200 (automatically appended by `QueryMapResult` iterator)
result = reef.query_map('System', 'Account', page_size=200, max_results=400)

for account, account_info in result:
    print(f"Free balance of account '{account.value}': {account_info.value['data']['free']}")

Create and send signed extrinsics

The following code snippet illustrates how to create a call, wrap it in a signed extrinsic and send it to the network:

from reefinterface import ReefInterface, Keypair
from reefinterface.exceptions import SubstrateRequestException

reef = ReefInterface(url="testnet")

keypair = Keypair.create_from_mnemonic('episode together nose spoon dose oil faculty zoo ankle evoke admit walnut')

call = reef.compose_call(
    call_module='Balances',
    call_function='transfer',
    call_params={
        'dest': '5E9oDs9PjpsBbxXxRE9uMaZZhnBAV38n2ouLB28oecBDdeQo',
        'value': 1 * 10**12
    }
)

extrinsic = reef.create_signed_extrinsic(call=call, keypair=keypair)

try:
    receipt = reef.submit_extrinsic(extrinsic, wait_for_inclusion=True)
    print("Extrinsic '{}' sent and included in block '{}'".format(receipt.extrinsic_hash, receipt.block_hash))

except SubstrateRequestException as e:
    print("Failed to send: {}".format(e))

The wait_for_inclusion keyword argument used in the example above will block giving the result until it gets confirmation from the node that the extrinsic is succesfully included in a block. The wait_for_finalization keyword will wait until extrinsic is finalized. Note this feature is only available for websocket connections.

Examining the ExtrinsicReceipt object

The reef.submit_extrinsic example above returns an ExtrinsicReceipt object, which contains information about the on-chain execution of the extrinsic. Because the block_hash is necessary to retrieve the triggered events from storage, most information is only available when wait_for_inclusion=True or wait_for_finalization=True is used when submitting an extrinsic.

Examples:

receipt = reef.submit_extrinsic(extrinsic, wait_for_inclusion=True)
print(receipt.is_success) # False
print(receipt.weight) # 216625000
print(receipt.total_fee_amount) # 2749998966
print(receipt.error_message['name']) # 'LiquidityRestrictions'

ExtrinsicReceipt objects can also be created for all existing extrinsics on-chain:

receipt = ExtrinsicReceipt(
    reef=reef,
    extrinsic_hash="0x56fea3010910bd8c0c97253ffe308dc13d1613b7e952e7e2028257d2b83c027a",
    block_hash="0x04fb003f8bc999eeb284aa8e74f2c6f63cf5bd5c00d0d0da4cd4d253a643e4c9"
)

print(receipt.is_success) # False
print(receipt.extrinsic.call_module.name) # 'Identity'
print(receipt.extrinsic.call.name) # 'remove_sub'
print(receipt.weight) # 359262000
print(receipt.total_fee_amount) # 2483332406
print(receipt.error_message['docs']) # [' Sender is not a sub-account.']

for event in receipt.triggered_events:
    print(f'* {event.value}')

Create mortal extrinsics

By default, immortal extrinsics are created, which means they have an indefinite lifetime for being included in a block. However, it is recommended to use specify an expiry window, so you know after a certain amount of time if the extrinsic is not included in a block, it will be invalidated.

extrinsic = reef.create_signed_extrinsic(call=call, keypair=keypair, era={'period': 64})

The period specifies the number of blocks the extrinsic is valid counted from current head.

Keypair creation and signing

mnemonic = Keypair.generate_mnemonic()
keypair = Keypair.create_from_mnemonic(mnemonic)
signature = keypair.sign("Test123")
if keypair.verify("Test123", signature):
    print('Verified')

By default, a keypair is using SR25519 cryptography, alternatively ED25519 can be explictly specified:

keypair = Keypair.create_from_mnemonic(mnemonic, crypto_type=KeypairType.ED25519)

Creating keypairs with soft and hard key derivation paths

mnemonic = Keypair.generate_mnemonic()
keypair = Keypair.create_from_uri(mnemonic + '//hard/soft')

By omitting the mnemonic the default development mnemonic is used:

keypair = Keypair.create_from_uri('//Alice')

Getting estimate of network fees for extrinsic in advance

keypair = Keypair(ss58_address="EaG2CRhJWPb7qmdcJvy3LiWdh26Jreu9Dx6R1rXxPmYXoDk")

call = reef.compose_call(
    call_module='Balances',
    call_function='transfer',
    call_params={
        'dest': 'EaG2CRhJWPb7qmdcJvy3LiWdh26Jreu9Dx6R1rXxPmYXoDk',
        'value': 2 * 10 ** 3
    }
)
payment_info = reef.get_payment_info(call=call, keypair=keypair)
# {'class': 'normal', 'partialFee': 2499999066, 'weight': 216625000}

Offline signing of extrinsics

This example generates a signature payload which can be signed on another (offline) machine and later on sent to the network with the generated signature.

• Generate signature payload on online machine:

reef = ReefInterface(url="testnet")

call = reef.compose_call(
    call_module='Balances',
    call_function='transfer',
    call_params={
        'dest': '5GrwvaEF5zXb26Fz9rcQpDWS57CtERHpNehXCPcNoHGKutQY',
        'value': 2 * 10**8
    }
)

era = {'period': 64, 'current': 22719}
nonce = 0

signature_payload = reef.generate_signature_payload(call=call, era=era, nonce=nonce)

• Then on another (offline) machine generate the signature with given signature_payload:

keypair = Keypair.create_from_mnemonic("nature exchange gasp toy result bacon coin broccoli rule oyster believe lyrics")
signature = keypair.sign(signature_payload)

• Finally on the online machine send the extrinsic with generated signature:

keypair = Keypair(ss58_address="5EChUec3ZQhUvY1g52ZbfBVkqjUY9Kcr6mcEvQMbmd38shQL")

extrinsic = reef.create_signed_extrinsic(
    call=call,
    keypair=keypair,
    era=era,
    nonce=nonce,
    signature=signature
)

result = reef.submit_extrinsic(
    extrinsic=extrinsic
)

print(result.extrinsic_hash)

Accessing runtime constants

All runtime constants are provided in the metadata (see reef.get_metadata_constants()), to access these as a decoded ScaleType you can use the function reef.get_constant():

constant = reef.get_constant("Balances", "ExistentialDeposit")

print(constant.value) # 10000000000

Cleanup and context manager

At the end of the lifecycle of a ReefInterface instance, calling the close() method will do all the necessary cleanup, like closing the websocket connection.

When using the context manager this will be done automatically:

with ReefInterface(url="testnet") as reef:
    events = reef.query("System", "Events")

# connection is now closed

Contact and Support

For questions, please reach out to us on our matrix chat group: Reef Developer Chat.