def set_symbols(pcontracts, dt_start='1980-1-1', dt_end='2100-1-1', n=None, spec_date={}):
 global _simulator
 _simulator = ExecuteUnit(pcontracts, dt_start, dt_end, n, spec_date)
 return _simulator

def set_symbols ( pcontracts , dt_start = '1980-1-1' , dt_end = '2100-1-1' , n = None , spec_date = { } ) : global _simulator _simulator = ExecuteUnit ( pcontracts , dt_start , dt_end , n , spec_date ) return _simulator
args: pcontracts : list of pcontracts dt_start : start time of all pcontracts dt_end : end time of all pcontracts n : last n bars spec_date : time range for specific pcontracts .