lst1 = [('vr1', '635', '1'), ('vr1', '32', '1'), ('vr1', '784', '0.526'), (
    'vr1', '431', '1')]
lst2 = [('vr1', '635', '3'), ('vr1', '784', '2.526'), ('vr1', '431', '2')]
d1 = {x[0:2]: x for x in lst1}
d2 = {x[0:2]: x for x in lst2}
for key in (set(d1) - set(d2)):
    pass
Obtain unique entries in column specific list comparison, efficiently