Hi Bo,
Grant is correct. When backtesting in minute mode or live trading, you can scan the prices and trading volumes of a maximum of 200 stocks. We need to enforce this cap to ensure algorithms can keep up with the flow of minute level market data. That being said, we are in the process of designing and API change that will allow you to screen for price/volume for a much larger universe before trading starts each day.
In research, you can scan as large a universe as you would like for price/volume. One of our engineers is currently working on porting get_fundamentals to research. Until that is done, you can import you own "shares outstanding" data. I know you can grab individual stock's shares outstanding historical data from Ycharts and Quandl. I'll be on the lookout for a publicly available market-wide dataset.
I don't have an exact timeline for either of these new features, but know that they are coming! Stay tuned for more details.
Andrew
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