python if else with a Flag not working correctly

Im trying to set a flag on my if else statement. I want it to be 1 if it crossover the upper thres but only the first cross after the previous signal and the same if it crossunder the lower thres (-1 on first cross under) . otherwise i want it to be 0.

So my logic is set a flag. Then on first sig cross (cond1) change the flag status... so it doesnt get triggered again.. but will now be able to trigger the signal cross under condition 2, otherwise its should be zero .. but it doens't work.

as is	how i want
1	1
1	-1
1	1
1	-1

def is_triggered(row):
    flag = False
    
    if  flag == False and  ((row.D  >  row.UPPER) and (row.D_PREV < row.UPPER)) :
        return  1
    flag = True
    
    if  flag == True and ((row.D  <  row.LOWER) and (row.D_PREV > row.LOWER)):
         return -1
    flag = False
    
    return 0