Web3.py – Resolving Unknown Account Error in web3.py Transact Function

I am able to use the web3.py library and i am able to deploy the contract directly using my node in ethereum.

I created my solidity code in remix and copied the abi in the etherum console to deploy the code. I got the address of the contract as well.

My solidity code is as follows.

pragma solidity ^0.4.0;

//For testing use the below data
//123,"wheat","grade1",50

contract bidding {

struct bid {
    string bidderName;
    uint grainId;
    uint bidAmount;
    uint bidTime;
}

mapping (uint => bid) bidInfos;
uint[] public bidIds;

function addBid(
    uint _bidId,
    string _bidderName, 
    uint _grainId, 
    uint _bidAmount
) public {
    var bid_info = bidInfos[_bidId];
    bid_info.bidderName = _bidderName;
    bid_info.grainId = _grainId;
    bid_info.bidAmount=_bidAmount;
    bid_info.bidTime= now;

    bidIds.push(_bidId) -1;
}

function getallBids() view public returns(uint[]) {
    return bidIds;
}

function getBid(uint _bidId) view public returns (string, uint, uint, uint) {
    return (
        bidInfos[_bidId].bidderName, 
        bidInfos[_bidId].grainId,
        bidInfos[_bidId].bidAmount, 
        bidInfos[_bidId].bidTime
    );
}

function getbidcount() view public returns (uint) {
    return bidIds.length;
}
}

I deployed in my etherum network and got the address as
In my python i am using the web3 library.

from web3 import Web3, HTTPProvider, IPCProvider, WebsocketProvider
import json
web3 = Web3(IPCProvider())
bid_abi=json.loads('''[{"constant":false,"inputs":[{"name":"_bidId","type":"uint256"},{"name":"_bidderName","type":"string"},{"name":"_grainId","type":"uint256"},{"name":"_bidAmount","type":"uint256"}],"name":"addBid","outputs":[],"payable":false,"stateMutability":"nonpayable","type":"function"},{"constant":true,"inputs":[],"name":"getallBids","outputs":[{"name":"","type":"uint256[]"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"_bidId","type":"uint256"}],"name":"getBid","outputs":[{"name":"","type":"string"},{"name":"","type":"uint256"},{"name":"","type":"uint256"},{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[],"name":"getbidcount","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"},{"constant":true,"inputs":[{"name":"","type":"uint256"}],"name":"bidIds","outputs":[{"name":"","type":"uint256"}],"payable":false,"stateMutability":"view","type":"function"}]''')

contract_bid=web3.eth.contract(abi=bid_abi,address='0xbcd8ffbb0f8a5410194ab5a3badf46caaa693098')

contract_bid.functions.addBid(10,"xyzz",1234,5600).transact()

This is the error i am getting.

  Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "D:\WinPython\python-3.5.4.amd64\lib\site-packages\web3\contract.py", line 1064, in transact
**self.kwargs)
  File "D:\WinPython\python-3.5.4.amd64\lib\site-packages\web3\contract.py", line 1341, in transact_with_contract_function
txn_hash = web3.eth.sendTransaction(transact_transaction)
  File "D:\WinPython\python-3.5.4.amd64\lib\site-packages\web3\eth.py", line 244, in sendTransaction
[transaction],
  File "D:\WinPython\python-3.5.4.amd64\lib\site-packages\web3\manager.py", line 106, in request_blocking
raise ValueError(response["error"])
 ValueError: {'code': -32000, 'message': 'unknown account'}

I am doing a web3.personal.unlockAccount as well. still it is giving same error.
There is only one account associated with my account as well. What am i doing wrong?

how to do the transaction so i can add a new bid from web3 in python and get the transaction hash.