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interactive brokers is really the best you're going to get. Its a low level API which is generally good. Terrible documentation, in fact the worst documentation I've ever seen on such a large project, but once you figure it out it'll give you all the functionality needed.

I like Alpaca. No fees and comes with a Python library called pylivetrader that is easy to use.

I use Interactive Brokers for the same purpose. They're pretty much your only option :)