Getting web3.exceptions.BadFunctionCallOutput on simple function call

• Version: 3.8.0
• Python: 2.7
• OS: linux

What was wrong?

I have a very simple contract in which I store a struct map

contract      A
{
    struct B
    {
        bool      set;
    }

    mapping (uint56 => B)   myMap;

    function isIn(uint56 _id) constant returns (bool)
    {
        return (myMap[_id].set);
    }
}

In another contract, I have an array of A contracts

  function isIn(uint56 _id) constant returns (bool)
    {
        uint  i = 0;
        while (arrayOfContractA[i] != 0)
            {
                if (A(arrayOfContractA[i]).isIn(_id))
                    return (true);
                i += 1;
            }
            return (false);
    }

When testing with truffle console, I’m getting normal return values like true of false. When I call the second isIn method from web3.py and I enter and _id that is registered, everything works well and I get True returned. But when I ask for an _id I didn’t registered, I get this :

web3.exceptions.BadFunctionCallOutput: Could not decode contract function call isIn return data 0x for output_types [u'bool']

I don’t understand how It could send someting different on false ?! Why do I have true and false in truffle (so web3.js), but not in web.py ? Is 0x returned when trying to return an uninitialised entry of a map ? I compiled my contract with solidity 0.4.4

Did this in web3.py

self._compiled = solc.compile_files([contractDir + "/A.sol", contractDir + "/B.sol", contractDir + "/B.sol"])
self._coreKey = contractDir + "/A.sol:A"
[...]
self._Core = self._web3.eth.contract(
                            abi=self._compiled[str(self._coreKey)]['abi'],
                            bytecode=self._compiled[str(self._coreKey)]['bin'],
                            bytecode_runtime=self._compiled[str(self._coreKey)]['bin-runtime'],
                            address=self._address)
[...]
self._Core.call().isIn(123)

and It crashes on the last line 😕

Thanks !

[mortimr]

Ok so I had to use transact instead of call, my bad again !

[mortimr]

Ok so I just added a return (false) at the beginning of my function and It’s working. I was doing something wrong by iterating through an array, uninitialised values inside it aren’t initialised to 0 as a map, my bad ! Now I have another problem where any method call that requires a transaction isn’t doing anything and I get no errors. Any hints on that ? 😕