def mean1(mylist):
   mysum = 0
   for i in range(len(mylist)):
      mysum += mylist[i]
   return float(mysum) / len(mylist)

def mean2(mylist):
   mysum = 0
   for value in mylist:
      mysum += value
   return float(mysum) / len(mylist)

def mean3(mylist):
   return float(sum(mylist)) / len(mylist)

mylist = [1, 2, 3, 4]
print mean1(mylist), mean2(mylist), mean3(mylist)