smartcontractkit/chainlink-mix

Working with smart contracts with eth-brownie, python, and Chainlink.

⚠️⚠️⚠️ This repo uses the eth-brownie development toolkit which is no longer maintained by its creators. Therefore this repo is not maintained actively either. we recommend you check out the Chainlink starter kits to find other repos that you can use to get started quickly. We recommend the use of the Hardhat or Foundry starter kits for most use cases.

chainlink-mix

NOTE: The new default is Sepolia. NOTE: This has been recently updated for better compatibility with local blockchains. Check out the scripts to learn more.

This is a repo to work with and use Chainlink smart contracts in a python environment. If you're brand new to Chainlink, check out the beginner walk-through in remix to learn the basics.

You can also check out the more advanced Chainlink tutorials there as well.

• chainlink-mix
  • Prerequisites
  • Installation
  • Testnet Development
  • Local Development
  • Running Scripts and Deployment
    • Chainlink Price Feeds
    • Chainlink VRF
    • Chainlink API Call
    • Chainlink Automation Deployment
    • Local Development
  • Testing
    • To test development / local
    • To test mainnet-fork
    • To test a testnet
  • Adding additional Chains
  • Linting
  • Resources
  • License

Prerequisites

Please install or have installed the following:

• nodejs and npm
• python

Installation

1. Install Brownie, if you haven't already. Here is a simple way to install brownie.

python3 -m pip install --user pipx
python3 -m pipx ensurepath
# restart your terminal
pipx install eth-brownie

Or, if that doesn't work, via pip

pip install eth-brownie

2. Download the mix and install dependencies.

brownie bake chainlink-mix
cd chainlink-mix
pip install -r requirements.txt

This will open up a new Chainlink project. Or, you can clone from source:

git clone https://github.com/PatrickAlphaC/chainlink-mix
cd chainlink-mix

Testnet Development

If you want to be able to deploy to testnets, do the following.

Set your WEB3_INFURA_PROJECT_ID, and PRIVATE_KEY environment variables.

You can get a WEB3_INFURA_PROJECT_ID by getting a free trial of Infura. At the moment, it does need to be infura with brownie. If you get lost, you can follow this guide to getting a project key. You can find your PRIVATE_KEY from your ethereum wallet like metamask.

You'll also need testnet ETH and LINK. You can get LINK and ETH into your wallet by using the faucets located here. If you're new to this, watch this video.. Look at the sepolia section for those specific testnet faucets.

You can add your environment variables to a .env file. You can use the .env.example as a template, just fill in the values and rename it to '.env'. Then, uncomment the line # dotenv: .env in brownie-config.yaml

Here is what your .env should look like:

export WEB3_INFURA_PROJECT_ID=<PROJECT_ID>
export PRIVATE_KEY=<PRIVATE_KEY>

AND THEN RUN source .env TO ACTIVATE THE ENV VARIABLES (You'll need to do this every time you open a new terminal, or learn how to set them easier)

WARNING

DO NOT SEND YOUR PRIVATE KEY WITH FUNDS IN IT ONTO GITHUB

Otherwise, you can build, test, and deploy on your local environment.

Local Development

For local testing install ganache-cli

npm install -g ganache-cli

or

yarn add global ganache-cli

All the scripts are designed to work locally or on a testnet. You can add a ganache-cli or ganache UI chain like so:

brownie networks add Ethereum ganache host=http://localhost:8545 chainid=1337

And update the brownie config accordingly. There is a deploy_mocks script that will launch and deploy mock Oracles, VRFCoordinators, Link Tokens, and Price Feeds on a Local Blockchain.

Running Scripts and Deployment

This mix provides a simple template for working with Chainlink Smart Contracts. The easiest way to start is to fork the mainnet chain to a local ganache chain. This will allow you to deploy local smart contracts to interact with the Chainlink Price Feeds.

NOTE: It's highly encouraged that you work with a local chain before testing on a testnet. You'll be a much faster developer!

If Sepolia network is not added to brownie by default, run:

brownie networks add Ethereum sepolia host=https://sepolia.infura.io/v3/$WEB3_INFURA_PROJECT_ID chainid=11155111 explorer=https://sepolia.etherscan.io/

Chainlink Price Feeds

This will deploy a smart contract to Sepolia and then read you the latest price via Chainlink Price Feeds.

brownie run scripts/price_feed_scripts/01_deploy_price_consumer_v3.py --network sepolia
brownie run scripts/price_feed_scripts/02_read_price_feed.py --network sepolia

Or, you can use ENS

brownie run scripts/price_feed_scripts/02_read_price_feed_with_ens.py --network sepolia

Otherwise, you can fork mainnet and use that in a local ganache development environment.

brownie console --network mainnet-fork
>>> price_feeds = PriceFeedConsumer.deploy('0x5f4eC3Df9cbd43714FE2740f5E3616155c5b8419', {'from': accounts[0]})
.
.
>>> latest_price = price_feeds.getLatestPrice()
>>> latest_price
59169208540

You can also use ENS to get prices. See the ens price feed script for more information.

Chainlink VRF

This will deploy a smart contract to Sepolia and get a Random number via Chainlink VRF.

If you haven't created and funded a subscription on vrf.chain.link you can do so on the UI, or by running:

brownie run scripts/vrf_scripts/create_subscription.py --network sepolia

Before running the next scripts. Running 01_deploy_vrf will also add your consumer contract to the registry.

brownie run scripts/vrf_scripts/01_deploy_vrf_consumer.py --network sepolia
brownie run scripts/vrf_scripts/02_request_randomness.py --network sepolia
brownie run scripts/vrf_scripts/03_read_random_number.py --network sepolia

Chainlink API Call

This will deploy a smart contract to Sepolia and then make an API call via Chainlink API Call.

brownie run scripts/chainlink_api_scripts/01_deploy_api_consumer.py --network sepolia
brownie run scripts/chainlink_api_scripts/02_request_api.py --network sepolia
brownie run scripts/chainlink_api_scripts/03_read_data.py --network sepolia

Chainlink Automation Deployment

This is just to show you how to deploy the Automation Compatible contracts, you can learn more about registering & using them in the Automate Contracts section of the Chainlink documentation.

brownie run scripts/automation_scripts/01_deploy_automation_counter.py --network sepolia
brownie run scripts/automation_scripts/02_check_upkeep.py --network sepolia

Local Development

For local development, you might want to deploy mocks. You can run the script to deploy mocks. Depending on your setup, it might make sense to not deploy mocks if you're looking to fork a mainnet. It all depends on what you're looking to do though. Right now, the scripts automatically deploy a mock so they can run.

Testing

brownie test

For more information on effective testing with Chainlink, check out Testing Smart Contracts

Tests are really robust here! They work for local development and testnets. There are a few key differences between the testnets and the local networks. We utilize mocks so we can work with fake oracles on our testnets.

There is a test_unnecessary folder, which is a good exercise for learning some of the nitty-gritty of smart contract development. It's overkill, so pytest will skip them intentionally. It also has a test_samples folder, which shows an example Chainlink API call transaction receipt.

To test development / local

brownie test

To test mainnet-fork

This will test the same way as local testing, but you will need a connection to a mainnet blockchain (like with the infura environment variable.)

brownie test --network mainnet-fork

To test a testnet

Sepolia is currently supported. Please check the Chainlink docs for which products are supported on which chains.

brownie test --network sepolia

Adding additional Chains

If the blockchain is EVM Compatible, adding new chains can be accomplished by something like:

brownie networks add Ethereum binance-smart-chain host=https://bsc-dataseed1.binance.org chainid=56

or, for a fork:

brownie networks add development binance-fork cmd=ganache-cli host=http://127.0.0.1 fork=https://bsc-dataseed1.binance.org accounts=10 mnemonic=brownie port=8545

Linting

pip install black
pip install autoflake
autoflake --in-place --remove-unused-variables --remove-all-unused-imports -r .
black .

If you're using vscode and the solidity extension, you can create a folder called .vscode at the root folder of this project, and create a file called settings.json, and add the following content:

{
  "solidity.remappings": [
    "@chainlink/=[YOUR_HOME_DIR]/.brownie/packages/smartcontractkit/chainlink-brownie-contracts@0.2.2",
    "@openzeppelin/=[YOUR_HOME_DIR]/.brownie/packages/OpenZeppelin/openzeppelin-contracts@4.3.2"
  ]
}

This will quiet the linting errors it gives you.

Resources

To get started with Brownie:

• Chainlink Documentation
• Check out the Chainlink documentation to get started from any level of smart contract engineering.
• Check out the other Brownie mixes that can be used as a starting point for your own contracts. They also provide example code to help you get started.
• "Getting Started with Brownie" is a good tutorial to help you familiarize yourself with Brownie.
• For more in-depth information, read the Brownie documentation.

Any questions? Join our Discord

License

This project is licensed under the MIT license.