Yahoo price data might not be good enough, certainly not for institutional level. I've found a number of serious errors in the past, including completely wrong dividends/adjusted prices for e.g. British American Tobacco (BATS.L), a major global international Tobacco firm listed in London. I am interested in this too: how can one use external price sources and stock tickers with zipline? There comes a point where it might be simpler just to write one's own backtester, and indeed, Zipline is slow, but there are advantages to using zipline as effectively an outsourced backtesting package: it will only get better with time, is tested by users, and enables you to quickly implement and combine sophisticated quant algos quite easily. It seems optically an attractive proposition for a startup family office who are hybrid quant (quant screening + overlay to fundamental equity research strategy), who want to grow without spending 100ks on hiring quant teams, database administators, months of dev time etc. to reinvent the wheel, but wish to remain 100% in control of every aspect of their research process. Factset etc. are OK but suffer from a variety of ball-aching limitations (not least, intentionallyno proper documentation , and support staff are crap for advanced stuff) and essentially again you have to build everything bottom up. Quantopian is top down, you can focus on the actual research and algorithms which is pretty powerful, and how things ought to be done.