Trying an algo with various symbols, error messages occur when a current symbol matches a previous instance (symbol was repurposed).
Since it seems there should never be two securities that use the same symbol (one is always defunct), requesting the default behavior be changed to simply run with the one that is currently trading and ignore the old one. We can automatically steer away from companies that have for example gone out of business and not need to worry that they once existed.
For the rare instance where the user might want to be testing against something in the distant past and no longer valid, an option will remain open to them, in that case they can go thru that process of invoking set_symbol_lookup_date().
This means for example if a user is testing with DAL (Delta Airlines), they are fine if the start date is no earlier than 2007-04-25 when that current symbol came online, and even before that there would simply be no data for DAL. If they go back to before 2006-02-02 when the previous symbol ended there would also simply be no data however they can test using the stale symbol via set_symbol_lookup_date().
Error There are multiple securities that have used the symbol DAL. You must use set_symbol_lookup_date() before using symbol(). The table below shows when each company traded using the symbol DAL. Learn More SECURITY FIRST TRADED LAST TRADED DELTA AIR LINES INC DEL 1993-01-03 2005-10-11 DELTA AIR LINES INC 2007-04-25 2014-10-14