# ink! contract interfacing
ink! is a programming language for smart contracts; blockchains built with the Substrate framework can choose from a 
number of smart contract languages which one(s) they want to support. ink! is one of them. It is an opinionated 
language that we have built by extending the popular Rust programming language with functionality needed to make 
it smart contract compatible.

[More information about ink!](https://use.ink/)

## Deploy a contract 

Tested on [substrate-contracts-node](https://github.com/paritytech/substrate-contracts-node) with the [Flipper contract from the tutorial](https://docs.substrate.io/tutorials/smart-contracts/prepare-your-first-contract/):

```python
substrate = SubstrateInterface(
    url="ws://127.0.0.1:9944",
    type_registry_preset='canvas'
)

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

# Deploy contract
code = ContractCode.create_from_contract_files(
    metadata_file=os.path.join(os.path.dirname(__file__), 'assets', 'flipper.json'),
    wasm_file=os.path.join(os.path.dirname(__file__), 'assets', 'flipper.wasm'),
    substrate=substrate
)

contract = code.deploy(
    keypair=keypair,
    endowment=0,
    gas_limit=1000000000000,
    constructor="new",
    args={'init_value': True},
    upload_code=True
)

print(f'✅ Deployed @ {contract.contract_address}')
```

## Work with an existing instance:

```python
# Create contract instance from deterministic address
contract = ContractInstance.create_from_address(
    contract_address=contract_address,
    metadata_file=os.path.join(os.path.dirname(__file__), 'assets', 'flipper.json'),
    substrate=substrate
)
```

## Read data from a contract:

```python
result = contract.read(keypair, 'get')
print('Current value of "get":', result.contract_result_data)
```

## Execute a contract call

```python
# Do a gas estimation of the message
gas_predit_result = contract.read(keypair, 'flip')

print('Result of dry-run: ', gas_predit_result.value)
print('Gas estimate: ', gas_predit_result.gas_required)

# Do the actual call
print('Executing contract call...')
contract_receipt = contract.exec(keypair, 'flip', args={

}, gas_limit=gas_predit_result.gas_required)

if contract_receipt.is_success:
    print(f'Events triggered in contract: {contract_receipt.contract_events}')
else:
    print(f'Error message: {contract_receipt.error_message}')
```

See complete [code example](https://github.com/polkascan/py-substrate-interface/blob/master/examples/create_and_exec_contract.py) for more details