Checkout quantopian.
They have a great API with a great backtester (zip line) and historical data.
All for free.
Their live trading is still in beta.
So how can a public service help you to develop a trading system with a difficult to learn language like python when every little detail has to be programmed? Maybe it is a wonderful system but traders should devote their time coming up with ideas to test, not with programming them. Tradestation is a good service for traders. If no account is required, a cheap but very powerful software like Amibroker is all you need. Why going public? If one cannot afford the $200 expense for Amibroker or some other backtesting platform then better forget about trading. The more secretive one is with his development, the better the chances of making money.