----- Asking for python version  -----

Suppose I want to only initialize with "SPY"

1.- How can I add new stocks during the day when "OnData" is executing? for example AMZN,NFLX,AAPL (suppose they are avalaibles from an external file).

2.- will they be available inmediately( in backtest and in live)?.

3.- How can I remove those symbols at the end of the day?.