Without detail, it's hard to say what's wrong but this you can create a buy order for $LEO.

import json from lighthive.client import Client from lighthive.datastructures import Operation accountname = '' active_key = '' symbol = 'leo' amount = 1 price = 0.01 lighthiveClient = Client(keys=[active_key]) payLoad = [{"contractName":"market","contractAction":"buy","contractPayload":{"symbol":symbol.upper(),"quantity":str(amount),"price":str(price)}}] jsonData = { 'required_auths': [accountname] ,'required_posting_auths': [] ,'id':'ssc-mainnet-hive' ,'json': json.dumps(payLoad) } op = Operation(type='custom_json', value=jsonData) r = lighthiveClient.broadcast_sync(op)