In Brownie, is there a way to define a constant in one place and use it in both a Vyper smart contract and a test script?

Question

I'm looking for something like an environment variable or a #define where the constant value gets substituted into the smart contract prior to compilation.

I have carefully read through the Brownie docs and found nothing but this seems like something that should exist.

What is it you're trying to achieve? Why does it need to be before compilation and not just passed in as a constructor argument? — The Ref, May 20 '22 at 12:02

Alec Stewart · Answer 1 · 2022-05-21T04:45:05.257

I ended up writing a Python function that reads the contract and extracts constant definitions from it into a dictionary that can be used by other Python scripts:

import re


def get_integer_constant_definitions_from_contract(contract_path):
    """Searches through a smart contract for constant declarations.

    Args:
        contract_path: The file path of the contract to search.

    Returns: A dictionary whose keys are the constant names and whose values
        are the corresponding constant values.

    """

    contract = open(contract_path, "r")
    contract_text = contract.read()

    # Matches constants with names in all caps and base 10 integer values.
    p = re.compile("(^[A-Z][A-Z_]+).*=[ ]?([0-9]+)[ ]*$", re.MULTILINE)
    base_10_matches = p.findall(contract_text)

    constants = {}
    for match in base_10_matches:
        constants[match[0]] = int(match[1])

    # Matches constants with names in all caps and hex integer values.
    p = re.compile("(^[A-Z][A-Z_]+).*=[ ]?(0[Xx][0-9A-Fa-f]+)[ ]*$", re.MULTILINE)
    hex_matches = p.findall(contract_text)

    for match in hex_matches:
        constants[match[0]] = int(match[1], 16)

    return constants

In Brownie, is there a way to define a constant in one place and use it in both a Vyper smart contract and a test script?

1 Answers1