Web3.py

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A python implementation of web3.js

• Python 2.7, 3.4, 3.5 support

Installation

pip install web3

Testing

For testing you can use the TestRPCProvider. This depends on eth-testrpc>=0.9.0 which must be eithe installed independently or with the following installation command.

pip install web3[tester]

Then in your code:

from web3 import Web3, TestRPCProvider

# Initialising a Web3 instance with an RPCProvider:
web3rpc = Web3(TestRPCProvider())

# or specifying host and port.
web3rpc = Web3(TestRPCProvider(host="127.0.0.1", port="8545"))

The TestRPCProvider uses an EVM backed by the ethereum.tester module from the pyethereum package. This can be quite useful for testing your code which uses web3.py.

Setting defaults

web3.eth.defaultAccount = <your (unlocked) account>
web3.eth.defaultBlock = "latest"
# Can also be an integer or one of "latest", "pending", "earliest"

Interacting with contracts

>>> abi = json.joads("<abi-json-string>")
>>> ContractFactory = web3.eth.contract(abi, code="0x...")
>>> ContractFactory.deploy()
... '0x461e829a731d96539ec1f147232f1d52b475225ed343e5853ff6bf3b237c6e79'
>>> contract = web3.eth.contract(abi, address="0x...")
>>> contract.transact().someMethod()
... '0xfbb0f76aa6a6bb8d178bc2b54de8fc7ca778d704af47d135c188ca7b5d25f2e4'
>>> contract.call().return13()
... 13
>>> contract.estimateGas().someMethod()
... 23212

You can listen for events using the on and pastEvents functions on a contract.

def transfer_callback(log_entry):
    ...  # do something with the log.

# create a filter and register a callback.
filter = MyContract.on("Transfer", {})
filter.watch(transfer_callback)

filter.stop_watching()

The underlying asynchronous operations are managed by gevent.

Timeouts, blocking and nonblocking requests

Web3.py does not currently support asynchronous calling patterns.