Celo's ContractKit is a library to help developers and validators to interact with the celo-blockchain.
ContractKit supports the following functionality:
- Connect to a node
- Access web3 object to interact with node's Json RPC API
- Send Transaction with celo's extra fields: (feeCurrency)
- Simple interface to interact with CELO and cUSD
- Simple interface to interact with Celo Core contracts
- Utilities
To install:
pip install .You need in Python version 3.8 or higher.
To start working with python contractkit you need a Kit instance:
from celo_sdk.kit import Kit
kit = Kit('https://alfajores-forno.celo-testnet.org')To access web3:
kit.w3.eth.getBalance(some_address)Kit allows you to set default transaction options:
from celo_sdk.kit import Kit
kit = Kit('https://alfajores-forno.celo-testnet.org')
currency_address = kit.base_wrapper.registry.load_contract_by_name('StableToken')['address']
kit.wallet_fee_currency = currency_addresscelo-blockchain has two initial coins: CELO and cUSD (stableToken). Both implement the ERC20 standard, and to interact with them is as simple as:
gold_token = kit.base_wrapper.create_and_get_contract_by_name('GoldToken')
balance = gold_token.balance_of(address)To send funds:
one_gold = kit.w3.toWei(1, 'ether')
tx_hash = gold_token.transfer(address, one_gold)To interact with cUSD, is the same but with a different contract:
stable_token = kit.base_wrapper.create_and_get_contract_by_name('StableToken')If you would like to pay fees in cUSD, set the gas price manually:
stable_token = kit.base_wrapper.create_and_get_contract_by_name('StableToken')
gas_price_contract = kit.base_wrapper.create_and_get_contract_by_name('GasPriceMinimum')
gas_price_minimum = gas_price_contract.get_gas_price_minimum(stable_token.address)
gas_price = int(gas_price_minimum * 1.3) # Wiggle room if gas price minimum changes before tx is sent
kit.wallet_fee_currency = stable_token.address # Default to paying fees in cUSD
kit.wallet_gas_price = int(gas_price)
tx = stable_token.transfer(recipient, wei_transfer_amount)Apart from GoldToken and StableToken, there are many core contracts.
For the moment, we have contract wrappers for:
- Accounts
- Attestations
- BlockchainParameters
- DoubleSigningSlasher
- DowntimeSlasher
- Election
- LockedGold
- Escrow
- Exchange
- Freezer
- GasPriceMinimum
- GoldToken
- Governance
- MultiSig
- Reserve
- ReleaseGold
- SortedOracles
- StableToken
- Validators
To create object of contract wrapper you shold set one of those contract names as a parameter to function BaseWrapper.create_and_get_contract_by_name(...)
Celo Core Contracts addresses, can be obtained by looking at the Registry contract.
That's actually how BaseWrapper obtain them.
We expose the registry api, which can be accessed by:
gold_token_address = kit.base_wrapper.registry.load_contract_by_name('GoldToken')['address']Wallet object by defaut generate some private key
But of course you can add your own already generated private key or generate new one
To add your own:
from celo_sdk.kit import Kit
kit = Kit('https://alfajores-forno.celo-testnet.org')
kit.wallet_add_new_key = '0xf2f48ee19680706196e2e339e5da3491186e0c4c5030670656b0e0164837257d'To generate new one:
new_key = kit.generate_new_key()
kit.wallet_add_new_key = new_keyTo see all the wallet accounts:
accounts = kit.wallet.accountsAnd to switch between accounts:
kit.wallet_change_account = existing_account_address # address of account has to be in wallet.__accounts dictIn addition to signing the transaction, the wallet can sign messages:
from celo_sdk.kit import Kit
from celo_sdk.celo_account.messages import encode_defunct
kit = Kit('https://alfajores-forno.celo-testnet.org')
message = kit.w3.soliditySha3(['address'], [signer]).hex() # For example we want to sign someones address
message = encode_defunct(hexstr=message)
signature = kit.wallet.active_account.sign_message(message)
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