cromewar / chainlink-mix

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

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

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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 walkthroughs in remix to learn the basics.

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


Please install or have installed the following:


  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
  1. Download the mix and install dependancies.
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
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 rinkeby and kovan sections for those specific testnet faucets.

You can add your environment variables to a .env file. You can use the .env.exmple 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:


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



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

Local Development

For local testing install ganache-cli

npm install -g ganache-cli


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!

Chainlink Price Feeds

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

brownie run scripts/price_feed_scripts/ --network kovan
brownie run scripts/price_feed_scripts/ --network kovan

Or, you can use ENS

brownie run scripts/price_feed_scripts/ --network kovan

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

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 kovan and get a Random number via Chainlink VRF.

brownie run scripts/vrf_scripts/ --network kovan
brownie run scripts/vrf_scripts/ --network kovan
brownie run scripts/vrf_scripts/ --network kovan

Chainlink API Call

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

brownie run scripts/chainlink_api_scripts/ --network kovan
brownie run scripts/chainlink_api_scripts/ --network kovan
brownie run scripts/chainlink_api_scripts/ --network kovan

Chainlink Keeper Deployment

This is just to show you how to deploy the Keepers, you can learn more about registering them in the Chainlink Keeper documenation.

brownie run scripts/keeper_scripts/ --network kovan
brownie run scripts/keeper_scripts/ --network kovan

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.


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 exersize 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

Kovan and Rinkeby are currently supported

brownie test --network kovan

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= chainid=56

or, for a fork:

brownie networks add development binance-fork cmd=ganache-cli host= fork= accounts=10 mnemonic=brownie port=8545


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": [

This will quiet the linting errors it gives you.


To get started with Brownie:

Any questions? Join our Discord


This project is licensed under the MIT license.

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

License:MIT License


Language:Solidity 56.2%Language:Python 43.1%Language:Shell 0.7%