Ethereum Smart Function Call Not Working: Python vs Truffle Dev

As a developer building decentralized applications (dApps) on the Ethereum network using smart contracts, you’re probably no stranger to the complexities of interacting with the blockchain. However, when it comes to calling specific functions from external scripts, errors can be frustrating and difficult to troubleshoot.

In this article, we’ll explore why an AddDeviceOwner function call may not work as expected in a Python script, despite success in the Truffle Dev console environment.

The Problem

Suppose you have a smart contract deployed to Ethereum that defines an AddDeviceOwner function. You want to write a Python script to call this function and test its functionality. Here’s what happens when you try to run the code:

import web3









Assuming w3 is your Web3 instance
w3 = web3.Web3()

Deploying the contract (replace with your actual deployment logic)
contract = w3.eth.contract(address="0x...", abi={"function": "AddDeviceOwner"}) 
Replace with your contract code

The AddDeviceOwner function takes two parameters: owner and newOwner. When you call this function in Truffle Dev, it should execute successfully. However, if something goes wrong in the Python script, you won’t see any errors or warnings. The function simply returns nothing.

The Problem

In your Python code, you are trying to access the contract instance with w3 = web3.Web3(), and then try to call the AddDeviceOwner function with contract = w3.eth.contract(address="0x..." , abi={"function": "AddDeviceOwner"}). However, since the Truffle Dev environment has already deployed your contract to the testnet, it does not have an instance of the smart contract. Therefore, trying to create a new instance using w3 is unnecessary and will throw an error.

Solution

To fix this, you need to modify your Python script to use Truffle Dev’s deployment logic instead of creating a new instance of the contract. Here’s how to do it:

import web3

Import required libraries from Truffle
from truffle.test import TestProvider
from contract import Contract
Replace with your actual contract code

Configure Truffle Dev provider
test_provider = TestProvider()

Deploy contract (replace with your actual deployment logic)
contract = Contract.from_abi("path/to/your/contract.abi", test_provider, "0x...", {"function": "AddDeviceOwner"}) 
Replace with your contract code

Now you can call the AddDeviceOwner function
result = contract.addDeviceOwner("owner", "newOwner")
print(result)

In this revised script, we import the TestProvider class from the Truffle library and use it to deploy the contract. The resulting contract instance is then used to call the AddDeviceOwner function.

Additional Tips

To ensure that your smart contracts are deployed correctly in the first place, you should:

• Use the correct ABI (Application Binary Interface) for your contract.

• Configure a Truffle Dev provider with the correct settings for your local network or testnet.

• Deploy the contract using a tool such as Truffle’s “truffle deploy” command.

By following these steps and modifying your Python script to use Truffle Dev’s deployment logic, you should be able to successfully call smart function calls from your Python scripts, even if they don’t work in the Truffle Dev console environment.