Zliczanie serii danych (z filtrowaniem?)

#!/usr/bin/env python

'''zliczanie wszystkich serii z pomoca defaultdict'''

import collections

a = [1,1,1,2,3,1,1,3,3,3,3,4,4,5,6,4,5,5]

results = collections.defaultdict(list)

prev = None

for i in a:
    if i != prev:
        results[i].append(0)
        prev = i

    results[i][-1] += 1

print results

# defaultdict(<type 'list'>, {1: [3, 2], 2: [1], 3: [1, 4], 4: [2, 1], 5: [1, 2], 6: [1]})

#----------------------------------------------------------------------

'''zliczanie wszystkich serii bez pomocy defaultdict'''

a = [1,1,1,2,3,1,1,3,3,3,3,4,4,5,6,4,5,5]

results = {}

prev = None

for i in a:
    if i != prev:
        if i not in results:
            results[i] = []
        results[i].append(0)
        prev = i

    results[i][-1] += 1

print results

# {1: [3, 2], 2: [1], 3: [1, 4], 4: [2, 1], 5: [1, 2], 6: [1]}

#----------------------------------------------------------------------

'''zliczanie serii z pominieciem serii jednoelementowych'''

a = [1,1,1,2,3,1,1,3,3,3,3,4,4,5,6,4,5,5]

results = {}

prev = None
count = 0

a.append(None) # wymaga dodatkowego oznaczenie konca listy

for i in a:
    if i != prev:
        if count > 1:
            if prev not in results:
                results[prev] = []
            results[prev].append(count)
        prev = i
        count = 0

    count += 1

print results

# {1: [3, 2], 3: [4], 4: [2], 5: [2]}

#----------------------------------------------------------------------