>>> from marks import perc_passed   

>>> l = [['44444444D',8.3],['11111111A',7.25],['88888888H',4.1],['22222222B',3.8],['66666666F',5.3]]
>>> round(perc_passed(l), 2)
60.0
>>> l = [['3A', 5]]
>>> round(perc_passed(l), 2)
100.0
>>> l = [['1A', 2], ['2B', 1], ['3C', 4]]
>>> round(perc_passed(l), 2)
0.0