How to do `abi.encodeWithSignature` in Python and eth-brownie

Question

I want to encode data using abi.encodeWithSignature in Python, and send the output from this into a contract function parameter. Now the problem is I can't figure out how should I do it.

The function I want to encode is like abi.encodeWithSignature("Increment(uint256)",55)

Answer 1

We can find teh equivalent bytes of abi.encodeWithSignature in Python and eth-brownie by using encode_input.

In the above example I had to find the encoding of Increment() and with uint256 parameter value of 55. Suppose the contract is deployed in test and stored in variable ContractA.

To find abi.encodeWithSignature I will write:

value = ContractA.Increment.encode_input(55)

Somehow it took me alot of time to find this, therefore I am writing this answer.

Answer 2

• I think there is some padding problem if we just do this ContractA.Increment.encode_input(55).
• This is the correct way to add padding. Say there is contract which has a function methodName.

value = Contract.methodName.encode_input()
print(value)
# wrong
>> '0xa7a7e4e8' 
value = Contract.methodName.encode_input()
# add padding to make it 32 bytes
value = value + "0" * (66 - len(value))
print(value)
# correct
>> '0xa7a7e4e800000000000000000000000000000000000000000000000000000000'