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(abi=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
abi = contract_interface['abi']
contract_instance = w3.eth.contract(address=contract_address, abi=abi,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

git clone [email protected]:ethereum/web3.py.git
cd web3.py

Please see OS-specific instructions for:

• Linux
• Mac
• Windows
• FreeBSD

Then run these install commands:

virtualenv venv
. venv/bin/activate
pip install -e .[dev]

For different environments, you can set up multiple virtualenv. For example, if you want to create a venvdocs, then you do the following:

virtualenv venvdocs
. venvdocs/bin/activate
pip install -e .[docs]
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 -v -s -r -1 web3/ tests/ ens/ -c "clear; flake8 web3 tests ens && echo 'flake8 success' || echo 'error'"

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

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

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

How to Execute the Tests?

1. Setup your development environment.

2. Execute tox for the tests

There are multiple components of the tests. You can run test to against specific component. For example:

# Run Tests for the Core component (for Python 3.5):
tox -e py35-core

# Run Tests for the Core component (for Python 3.6):
tox -e py36-core

If for some reason it is not working, add --recreate params.

tox is good for testing against the full set of build targets. But if you want to run the tests individually, py.test is better for development workflow. For example, to run only the tests in one file:

py.test tests/core/gas-strategies/test_time_based_gas_price_strategy.py

Release setup

For Debian-like systems:

apt install pandoc

To release a new version:

make release bump=$$VERSION_PART_TO_BUMP$$

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, specify which part to bump, like make release bump=minor or make release bump=devnum.

If you are in a beta version, make release bump=stage will switch to a stable.

To issue an unstable version when the current version is stable, specify the new version explicitly, like make release bump="--new-version 4.0.0-alpha.1 devnum"