df[16820:16830]
       data0  start_stop
16820      1           0
16821      1           1
16822      1           0
16823      1           0
16824      1           0
16825      1          -1
16826      0           0
16827      0           0
16828      1           1
16829      0           0
16830      1           1

data0  start_stop  valid
16820      1           0   False
16821      1           1   True
16822      1           0   True
16823      1           0   True
16824      1           0   True
16825      1          -1   False
16826      0           0   False
16827      0           0   False
16828      1           1   True
16829      0           0   True
16830      1          -1   False
...

df['valid'] = 'True'; df.loc[df['data0'] > df['data1'],'valid'] = 'False'