How can I get the hexadecimal equivalent for a method name in an Ethereum contract using Python?

Question

The function to call is called xyz().

My code:

web3.sha3("xyz()").substr(0,10)

Error:

AttributeError: module 'web3' has no attribute 'sha3'

In newer versions of web3, the above error occurs. What else can be used to get the hexadecimal equivalent of the function name?

Source of code: How to know the hex code to use in data to call a specific contract function? (the solution doesn't work on newer versions of web3)

Answer 1

The hexadecimal equivalent of the method is called the function selector.

The function selector is the first 4 bytes of Keccak hash of the function signature, arguments packed as string types.

You can get this by:

>>> from web3 import Web3
>>> Web3.keccak(text="xyz()")
HexBytes('0x356bc81e51224d094b17ccb8f80b1e659fe334bcf15c6240857cce0568cbb0ba')
>>> hex_bytes = Web3.keccak(text="xyz()")
>>> print(hex_bytes[0:4].hex())
0x356bc81e

Answer 2

you are looking for this:

encodeFunctionSignature

web3.eth.abi.encodeFunctionSignature(functionName);

Encodes the function name to its ABI signature, which are the first 4 bytes of the sha3 hash of the function name including types.

https://web3js.readthedocs.io/en/v1.2.11/web3-eth-abi.html

In pythhon there should exist an equivalent call