The Local RPC Client

Brownie is designed to use ganache-cli as a local development environment.

Launching and Connecting

The connection settings for the local RPC are outlined in brownie-config.yaml:

    reverting_tx_gas_limit: 6721975
        cmd: ganache-cli
        port: 8545
        gas_limit: 6721975
        accounts: 10
        evm_version: petersburg
        mnemonic: brownie

Brownie will launch or attach to the client when using any network that includes a test-rpc dictionary in it’s settings.

Each time Brownie is loaded, it will first attempt to connect to the host address to determine if the RPC client is already active.

Client is Active

If able to connect to the host address, Brownie:

  • Checks the current block height and raises an Exception if it is greater than zero
  • Locates the process listening at the address and attaches it to the Rpc object
  • Takes a snapshot

When Brownie is terminated:

  • The RPC client is reverted based on the initial snapshot.

Client is not Active

If unable to connect to the host address, Brownie:

  • Launches the client using the test-rpc command given in the configuration file
  • Waits to see that the process loads successfully
  • Confirms that it can connect to the new process
  • Attaches the process to the Rpc object

When Brownie is terminated:

  • The RPC client and any child processes are also terminated.

Common Interactions

You can interact with the RPC client using the Rpc object, which is automatically instantiated as rpc:

>>> rpc
< object at 0x7f720f65fd68>


To mine empty blocks, use rpc.mine.

>>> web3.eth.blockNumber
>>> rpc.mine(50)
Block height at 50
>>> web3.eth.blockNumber


You can call rpc.time to view the current epoch time. To fast forward, call rpc.sleep.

>>> rpc.time()
>>> rpc.sleep(100)
>>> rpc.time()


rpc.snapshot takes a snapshot of the current state of the blockchain:

>>> rpc.snapshot()
Snapshot taken at block height 4
>>> accounts[0].balance()
>>> accounts[0].transfer(accounts[1], "10 ether")

Transaction sent: 0xd5d3b40eb298dfc48721807935eda48d03916a3f48b51f20bcded372113e1dca
Transaction confirmed - block: 5   gas used: 21000 (100.00%)
<Transaction object '0xd5d3b40eb298dfc48721807935eda48d03916a3f48b51f20bcded372113e1dca'>

You can return to this state later using rpc.revert:

>>> accounts[0].balance()
>>> rpc.revert()
Block height reverted to 4
>>> accounts[0].balance()

Reverting does not consume a snapshot. You can return to the same snapshot as many times as needed. However, if you take a new snapshot the previous one is no longer accessible.

To return to the genesis state, use rpc.reset.

>>> web3.eth.blockNumber
>>> rpc.reset()
>>> web3.eth.blockNumber