mylist = [1,2,2,2,2,3,3,3,4,4,4,4]
myset = set(mylist)  #myset是另外一个列表，里面的内容是mylist里面的无重复 项
for item in myset:
  print("the %d has found %d" %(item,mylist.count(item)))

List=[1,2,2,2,2,3,3,3,4,4,4,4]
a = {}
for i in List:
  if List.count(i)>1:
    a[i] = List.count(i)
print (a)

>>> from collections import Counter
>>> Counter([1,2,2,2,2,3,3,3,4,4,4,4])
Counter({1: 5, 2: 3, 3: 2})

l=[1,4,2,4,2,2,5,2,6,3,3,6,3,6,6,3,3,3,7,8,9,8,7,0,7,1,2,4,7,8,9]

count_times = []
for i in l :
  count_times.append(l.count(i))

m = max(count_times)
n = l.index(m)

print (l[n])