How to submit a transaction form the root/sudo acount using python substrate interface

Question

I am using Python Substrate Interface (https://github.com/polkascan/py-substrate-interface) to interact with the substrate node.

I need to execute Pallet::Balances::force_transfer function, this function can only be run with the root/sudo account. How I can achieve this please.

Answer 1

You need to have the Sudo pallet deployed, which is often the case in development networks.
Then you can wrap the call in Sudo::sudo and sign it with the sudo key.

Example of Alice being sudo and stealing funds from Bob via sudo force_transfer;
You can try this code on a substrate --dev node to see it working.

from substrateinterface import SubstrateInterface, Keypair
from substrateinterface.exceptions import SubstrateRequestException

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

# Derive the Alice and Bob accounts
alice = Keypair.create_from_uri('//Alice')
bob = Keypair.create_from_uri('//Bob')

# Query the sudo key
sudo_key = substrate.query(
    module='Sudo',
    storage_function='Key',
)

print("Sudo key: {}".format(sudo_key.value))
if sudo_key.value == alice.ss58_address:
    print("Alice is the sudo key")
else:
    raise Exception("Unknown or no sudo key")

# Alice steals funds from Bob via sudo force_transfer:
call = substrate.compose_call(
    call_module='Balances',
    call_function='force_transfer',
    call_params={
        'source': bob.ss58_address,
        'dest': alice.ss58_address,
        'value': 100000000000000000000,
    }
)
# Wrap it in sudo.
call = substrate.compose_call(
    call_module='Sudo',
    call_function='sudo',
    call_params={
        'call': call.value,
    }
)

# Signed by Alice
extrinsic = substrate.create_signed_extrinsic(call=call, keypair=alice)

try:
    receipt = substrate.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))