Say I have the following SimpleMath solidity library defined as follows:

library SimpleMath {

  function add(uint a, uint b) internal pure returns(uint)
    return a + b;

How do I import this library using brownie in my python script and call the add method? I would like to run unit tests of library functions.

I don't seem to have an issue importing the library, however I can't access its functions even when changing the access modifier to public I get the following brownie error:

from brownie import SimpleMath

def test_add():
  retVal = SimpleMath.add(10, 20)
  assert retVal == 30

AttributeError: 'ContractContainer' object has no attribute 'add'

Edit: So apparently you have to deploy a library the same way you would deploy a contract and then access it's methods, however I can't access the library's internal methods only external/public:

simpleMath = SimpleMath.deploy({'from': account})
simpleMath = simpleMath.add() # since add is internal cannot access

AttributeError: Contract 'SimpleMath' object has no attribute 'add'

How then can I test a libraries functions that are internal in brownie?

  • Import it where? Is it in another file? Commented Jan 19, 2022 at 2:56
  • Hi Patrick, yes the same way I would import a contract called SimpleStorage in my python script and call it's methods.
    – MShakeG
    Commented Jan 19, 2022 at 5:15
  • If you are using hardhat, you can try hardhat-exposed. Although I haven't tried it yet Commented Jul 6, 2022 at 9:20

1 Answer 1


Since you can't access internal or private functions externally for both contracts and libraries I wrapped the method/s of the library SimpleMath in the method/s of a contract called TestSimpleMath, which has it's methods set to external, thus exposing the library method/s.

import { SimpleMath } from '.SimpleMath.sol';

contract TestSimpleMath {
  function add(uint a, uint b) external pure returns(uint) {
    return SimpleMath.add(a, b);

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