Deploying Contracts

Brownie lets you write scripts to interact with your project. Scripting is especially useful for deploying your contracts to the main-net, or for automating processes that you perform regularly.

Every script should begin with from brownie import *. This imports the instantiated project classes into the local namespace and gives access to the Brownie Brownie API in exactly the same way as if you were using the console.

To execute a script from the command line:

$ brownie run <script> [function]

Or from the console, use the run method:

>>> run('token') # executes the main() function within scripts/

Or the import statement:

>>> from scripts.token import main
>>> main()

Scripts are stored in the scripts/ folder. Each script can contain as many functions as you’d like. If no function name is given, brownie will attempt to run main.

Here is a simple example script from the token project, used to deploy the Token contract from contracts/Token.sol using web3.eth.accounts[0].

from brownie import *

def main():
    accounts[0].deploy(Token, "Test Token", "TEST", 18, "1000 ether")

See the Brownie API documentation for available classes and methods when writing scripts.

Unlinked Libraries

If a contract requires a library, the most recently deployed one will be used automatically. If the required library has not been deployed yet an UndeployedLibrary exception is raised.

>>> accounts[0].deploy(MetaCoin)
  File "brownie/network/", line 167, in __call__
    f"Contract requires '{library}' library but it has not been deployed yet"
UndeployedLibrary: Contract requires 'ConvertLib' library but it has not been deployed yet

>>> accounts[0].deploy(ConvertLib)
Transaction sent: 0xff3f5cff35c68a73658ad367850b6fa34783b4d59026520bd61b72b6613d871c
ConvertLib.constructor confirmed - block: 1   gas used: 95101 (48.74%)
ConvertLib deployed at: 0x08c4C7F19200d5636A1665f6048105b0686DFf01
<ConvertLib Contract object '0x08c4C7F19200d5636A1665f6048105b0686DFf01'>

>>> accounts[0].deploy(MetaCoin)
Transaction sent: 0xd0969b36819337fc3bac27194c1ff0294dd65da8f57c729b5efd7d256b9ecfb3
MetaCoin.constructor confirmed - block: 2   gas used: 231857 (69.87%)
MetaCoin deployed at: 0x8954d0c17F3056A6C98c7A6056C63aBFD3e8FA6f
<MetaCoin Contract object '0x8954d0c17F3056A6C98c7A6056C63aBFD3e8FA6f'>