devium / web3.py

A python interface for interacting with the Ethereum blockchain and ecosystem.

Web3.py

A Python implementation of web3.js

• Python 3.5+ support

Read more in the documentation on ReadTheDocs. View the change log on Github.

Quickstart

import json
import web3

from web3 import Web3, HTTPProvider, TestRPCProvider
from solc import compile_source
from web3.contract import ConciseContract

# Solidity source code
contract_source_code = '''
pragma solidity ^0.4.0;

contract Greeter {
    string public greeting;

    function Greeter() {
        greeting = 'Hello';
    }

    function setGreeting(string _greeting) public {
        greeting = _greeting;
    }

    function greet() constant returns (string) {
        return greeting;
    }
}
'''

compiled_sol = compile_source(contract_source_code) # Compiled source code
contract_interface = compiled_sol['<stdin>:Greeter']

# web3.py instance
w3 = Web3(TestRPCProvider())

# Instantiate and deploy contract
contract = w3.eth.contract(contract_interface['abi'], bytecode=contract_interface['bin'])

# Get transaction hash from deployed contract
tx_hash = contract.deploy(transaction={'from': w3.eth.accounts[0], 'gas': 410000})

# Get tx receipt to get contract address
tx_receipt = w3.eth.getTransactionReceipt(tx_hash)
contract_address = tx_receipt['contractAddress']

# Contract instance in concise mode
contract_instance = w3.eth.contract(contract_interface['abi'], contract_address, ContractFactoryClass=ConciseContract)

# Getters + Setters for web3.eth.contract object
print('Contract value: {}'.format(contract_instance.greet()))
contract_instance.setGreeting('Nihao', transact={'from': w3.eth.accounts[0]})
print('Setting value to: Nihao')
print('Contract value: {}'.format(contract_instance.greet()))

Developer setup

If you would like to hack on web3.py, set up your dev environment with:

sudo apt-get install libssl-dev
# ^ This is for Debian-like systems. TODO: Add more platforms

git clone [email protected]:ethereum/web3.py.git
cd web3.py
virtualenv venv
. venv/bin/activate
pip install -r requirements-dev.txt
pip install -e .

For different environments, you can set up multiple virtualenvs, like:

Python 3

virtualenv -p python3 venvpy3
. venvpy3/bin/activate
pip install -r requirements-dev.txt
pip install -e .

Docs

virtualenv venvdocs
. venvdocs/bin/activate
pip install -r requirements-dev.txt
pip install -e .

Using Docker

If you would like to develop and test inside a docker environment, use the sandbox container provided in the docker-compose.yml file.

To start up the test environment, run:

docker-compose up -d

This will build a docker container set up with an environment to run the Python test code.

Note: This container does not have go-ethereum installed, so you cannot run the go-ethereum test suite.

To run the Python tests from your local machine:

docker-compose exec sandbox bash -c 'pytest -n 4 -f -k "not goethereum"'

You can run arbitrary commands inside the docker container by using the bash -c prefix.

docker-compose exec sandbox bash -c ''

Or, if you would like to just open a session to the container, run:

docker-compose exec sandbox bash

Testing Setup

During development, you might like to have tests run on every file save.

Show flake8 errors on file change:

# Test flake8
when-changed -r web3/ tests/ -c "clear; git diff HEAD^ | flake8 --diff"

You can use pytest-watch, running one for every python environment:

pip install pytest-watch

cd venv
ptw --onfail "notify-send -t 5000 'Test failure ⚠⚠⚠⚠⚠' 'python 3 test on web3.py failed'" ../tests ../web3

#in a new console
cd venvpy2
ptw --onfail "notify-send -t 5000 'Test failure ⚠⚠⚠⚠⚠' 'python 2 test on web3.py failed'" ../tests ../web3

Or, you can run multi-process tests in one command, but without color:

# in the project root:
py.test --numprocesses=4 --looponfail --maxfail=1
# the same thing, succinctly:
pytest -n 4 -f --maxfail=1

Release setup

For Debian-like systems:

apt install pandoc

To release a new version:

bumpversion $$VERSION_PART_TO_BUMP$$
git push && git push --tags
make release

How to bumpversion

The version format for this repo is {major}.{minor}.{patch} for stable, and {major}.{minor}.{patch}-{stage}.{devnum} for unstable (stage can be alpha or beta).

To issue the next version in line, use bumpversion and specify which part to bump, like bumpversion minor or bumpversion devnum.

If you are in a beta version, bumpversion stage will switch to a stable.

To issue an unstable version when the current version is stable, specify the new version explicitly, like bumpversion --new-version 4.0.0-alpha.1 devnum