Part 3: Deploy to a Local Chain

At part 2 of the tutorial you created a local chain named ‘horton’. Now, we will deploy the Greeter contract to this chain.

Project Config

First, we have to add the chain to the project configuration file:

$ nano project.json

After edit, the project file should look like this:

    "contracts_source_dirs": ["./contracts"],
    "import_remappings": []
  "chains": {
    "horton": {
      "chain": {
        "class": "populus.chain.ExternalChain"
      "web3": {
        "provider": {
          "class": "web3.providers.ipc.IPCProvider",
        "settings": {
      "contracts": {
        "backends": {
          "JSONFile": {"$ref": "contracts.backends.JSONFile"},
          "ProjectContracts": {
            "$ref": "contracts.backends.ProjectContracts"

The ipc_path should be the exact ipc_path on your machine. If you are not sure, copy-paste the path from the script in the chains/horton/ directory.


Populus uses JSON schema configuration files, on purpose. We think that for blockchain development, it’s safer to use static, external configuration, than a Python module. For more about JSON based configuration see JSON Schema.

Note the line {"$ref": "contracts.backends.JSONFile"}. There is a $ref, but the reference key does not exist in the file. This is beacuase the project.json config file is complementary to the main populus user-scope config file, at ~/.populus/config.json. The user config holds for all your populus projects, and you can use the project.json just for the configuration changes that you need for a specific project. Thus, you can $ref the user-config keys in any project configuration file.

Running the Chain

If the horton chain is not running (see part 2), run it. From the project directory, in another terminal, use the script that Populus created:

$ chains/horton/./

You should see a ton of things that geth outputs.


Finally, deploy the contract:

$ populus deploy --chain horton Greeter --no-wait-for-sync

> Found 1 contract source files
  - contracts/Greeter.sol
> Compiled 1 contracts
  - contracts/Greeter.sol:Greeter
Beginning contract deployment.  Deploying 1 total contracts (1 Specified, 0 because of library dependencies).


Deploy Transaction Sent: 0x364d8d4b7e40992bed2ea5f92af833d58ef1b9f3b4171c1f64f8843c2527437d
Waiting for confirmation...

After a few seconds the transaction is mined in your local chain:

Transaction Mined
Tx Hash      : 0x364d8d4b7e40992bed2ea5f92af833d58ef1b9f3b4171c1f64f8843c2527437d
Address      : 0x1c51ff8a84345f0a5940601b3bd372d8105f71aa
Gas Provided : 465580
Gas Used     : 365579

Verified contract bytecode @ 0x1c51ff8a84345f0a5940601b3bd372d8105f71aa
Deployment Successful.

Well done!


We used here --no-wait-for-sync, since the account has (a lot of) Eth from the get go, allocated in the genesis block. However, if you work with testnet or mainnet, you must sync at least until the block with the transactions that sent some Eth to the account you are deploying from. Otherwise, your local geth will not know that there is Eth in the account to pay for the gas. Once the chain is synced, you can deploy immidiatly.