Goldman's core risk management system (SecDB) is written in python, as is JPMorgan's Athena and BofAs Quartz. I believe the main people responsible for SecDB implemented Athena at JP and then Quartz at BofA.
And the whole system is in part credited with helping them survive the recent financial crisis ... although simply listening to their risk people was more important. But it's all intertwingled, I'm sure, because good risk people would want a system like SecDB so they know the company's positions in quasi-real time with a great deal of assurance vs. hours and days and through e.g. scraping spreadsheets, often manually, etc.