I seem to be running the following error when I try to run this script: ,

from brownie import AdvancedCollectible, accounts, network, config

def main():
    dev = accounts.add(config['wallets']['from_key'])

My brownie-config.yaml:

# exclude SafeMath when calculating test coverage
# https://eth-brownie.readthedocs.io/en/v1.10.3/config.html#exclude_paths
    - SafeMath
  - smartcontractkit/[email protected]
  - OpenZeppelin/[email protected]
      - '@chainlink=smartcontractkit/[email protected]'
      - '@openzeppelin=OpenZeppelin/[email protected]'
dotenv: .env
  from_key: ${PRIVATE_KEY}
  from_mnemonic: ${MNEMONIC} 

The error:

brownie run scripts/advanced_collectible/deploy_advanced.py 

Brownie v1.14.3 - Python development framework for Ethereum

NftdemoProject is the active project.

Launching 'ganache-cli --port 8545 --gasLimit 12000000 --accounts 10 --hardfork istanbul --mnemonic brownie'...

Running 'scripts/advanced_collectible/deploy_advanced.py::main'...
  File "brownie/_cli/run.py", line 49, in main
    return_value, frame = run(
  File "brownie/project/scripts.py", line 103, in run
    return_value = f_locals[method_name](*args, **kwargs)
  File "./scripts/advanced_collectible/deploy_advanced.py", line 4, in main
    dev = accounts.add(config['wallets']['from_key'])
  File "brownie/network/account.py", line 132, in add
    w3account = web3.eth.account.from_key(private_key)
  File "eth_utils/decorators.py", line 18, in _wrapper
    return self.method(obj, *args, **kwargs)
  File "eth_account/account.py", line 246, in from_key
    key = self._parsePrivateKey(private_key)
  File "eth_utils/decorators.py", line 18, in _wrapper
    return self.method(obj, *args, **kwargs)
  File "eth_account/account.py", line 694, in _parsePrivateKey
    return self._keys.PrivateKey(HexBytes(key))
  File "hexbytes/main.py", line 23, in __new__
    bytesval = to_bytes(val)
  File "hexbytes/_utils.py", line 17, in to_bytes
    return hexstr_to_bytes(val)
  File "hexbytes/_utils.py", line 50, in hexstr_to_bytes
    return binascii.unhexlify(ascii_hex)
Error: Non-hexadecimal digit found

I made sure I have my keys set in my .env file as export PRIVATE_KEY='0x...", so why is it not able to pull the variable from it or am I missing some step here? Any advice would be appreciated. Thanks!

  • could you run echo $PRIVATE_KEY and verify that the private key is correct with the 0x appended? And could you add your brownie-config.yaml file to the question? Commented May 13, 2021 at 13:59
  • Updated with my brownie-config.yaml Just ran echo $PRIVATE_KEY but it didn't return anything, I did notice that my .env file seems to be getting read as plaintext by visualstudio... could that be the problem?
    – rizonpoint
    Commented May 14, 2021 at 18:50
  • Run source .env in your shell. Or add dotenv: .env to your brownie config Commented May 14, 2021 at 18:57
  • I already had dotenv: .env in my brownie config (interesting why that didn't work), so I tried to run source .env per your advice, and that seems to now return the correct key from my .env file when i run echo $PRIVATE_KEY. Double checked it to make sure i have it appended correctly, but still getting the non-hexadecimal digit error.
    – rizonpoint
    Commented May 14, 2021 at 20:17
  • Does it have the 0x at the front? Commented May 14, 2021 at 21:04

2 Answers 2


I have the same error on my Windows system. When i hardcoded my private key in brownie-config.yaml from_key: 0x... everything works fine. So, i think the problem in python part, when it tries to get variable. Also, trying to get value in console using echo $Env:PRIVATE_KEY works fine.


I just encountered the same error, what should fix it is the python package python-dotenv. Once you install it python should be able to read those .env files.

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