How could I return 'gasUsed' inside populus?

Question

I am using populus to experiment my contract. I want to return only gasUsed for my transaction but it returns complete summary of the transaction.

[Q] How could I obtain only gasUsed value or should I retrieve that value by trimming the string from the output.

test.py:

   def test_linkedlist(web3, accounts, chain, unmigrated_chain):
       my_contract       = unmigrated_chain.get_contract('Receipt');
       set_txn_hash     = my_contract.transact().push( 10, 20, 32 );
       receipt_txn_hash = unmigrated_chain.wait.for_receipt(set_txn_hash)

       print( receipt_txn_hash ); || print( web3.eth.getTransactionReceipt("0x1139cca78666519a834cf40670faa4f01324a04f0ec4e6072863bf4812598a5f") ); #both give the same output.

Output:

tests/test_greeter.py No handlers could be found for logger "testrpc.rpc"
/usr/local/lib/python2.7/site-packages/secp256k1/__init__.py:228: UserWarning: implicit cast from 'char *' to a different pointer type: will be forbidden in the future (check that the types are as you expect; use an explicit ffi.cast() if they are correct)
  self.ctx, res_compressed, outlen, self.public_key, compflag)
{'contractAddress': None, 'cumulativeGasUsed': 114325, 'logs': [], 
'blockHash': u'0xda17ffe52e074957420554fbf2e3fb86d1ff81db989c6bb50d22a88850ee9495',
 'transactionHash': u'0x1139cca78666519a834cf40670faa4f01324a04f0ec4e6072863bf4812598a5f', 
'blockNumber': 4, 'transactionIndex': 0, 'gasUsed': 114325}

I want to return only: 114325 ___________________________^

Thank you for your valuable time and help.

Answer 1

What web3.eth.getTransactionReceipt returns is a Python dictionary.

You can access Python dictonary items using the square bracket syntax:

 receipt = web3.eth.getTransactionReceipt("0x1139cca78666519a834cf40670faa4f01324a04f0ec4e6072863bf4812598a5f")
 gasUsed = receipt["gasUsed"]
 print(gasUsed)

For further information please see this Python tutorial.