Take a look at Counter 
from collections import Counter
a = ['a','a','b','b']
b = ['b','b','c','d']
c = a+b
cnt = Counter()
for x in c:
     cnt[x] +=1
print(cnt)
    Counter({'a': 2, 'b': 4, 'c': 1, 'd': 1})
The above will get you counts of each but it seems like you're more concerned at a list level.
from collections import defaultdict
f = defaultdict(list)
a = ['a','a','b','b']
b = ['b','b','c','d']
c = ['e','f','g','h']
d = a + b + c
 for i in d:
     f[i] = 0
     if i in b:
         f[i] += 1
     if i in c:
         f[i] +=1
     if i in a:
         f[i] +=1
print (f)
defaultdict(list,
                {'a': 1, 'b': 2, 'c': 1, 'd': 1, 'e': 1, 'f': 1, 'g': 1, 'h': 1})