Contract API

Provides a wrapper around PyEvm and PyAbi and is the easiest way to interact with Contracts. Solidity contract methods are extracted from the ABI and made available as attributes on the instance of the Contract.

For example, if a Solidity contract defines the following methods:

function hello(address caller) public returns (bool){}

function world(string name) view (string)

they will be automatically available in the instance of the Contract like this:

# write call to the hello method
contract.hello.transact("0x11", caller="0x..")

# read call to world method
contract.world.call("dave")

Each method name is an attribute on the instance of Contract. To invoke them, you need to append either:

# this is a write/transaction
# where:
# - args: is 0 of more expected arguments to the method
# - caller: is the address of the account calling the method
# - value: is an optional value in Ether 
.transact(*args, caller: str, value: int=0)

# this is a read (view) call
# where:
# - args: is 0 of more expected arguments to the method
.call(*args)

Under the covers, a Contract knows how to properly encode all interactions with the EVM, and likewise decode any return values.

Constructor

Create an instance of a Contract from an ABI.

See Utilities for a simpler way to create a Contract

def __init__(self, evm: PyEvmLocal | PyEvmFork, abi: PyAbi)

Parameters

  • evm an instance of one of the EVMs
  • abi an instance of PyAbi

Returns self (Contract)

Example:

evm = PyEvmLocal()
abi = PyAbi.load_from_json(...)
counter = Contract(evm, abi)

Methods

at

Set the contract address. Note: this is automatically set when using deploy

def at(self, address: str) -> Contract

Parameters

  • address the address of the Contract in the EVM

Returns self

Example:

contract.at('0x11...')

deploy

Deploy the contract, returning it's address

def deploy(self, caller: str, args=[], value: int = 0) -> str

Parameters

  • caller: the address of the requester...msg.sender
  • args: a list of args expected by the Contract's constructor (if any)
  • value: optional amount of Ether for the contract

Returns the address of the deployed contract

Example:

# deploy a contract that's expecting 
# no constructor arguments and no initial balance
contract.deploy(caller='0x11...')