dict_word = collections.defaultdict(int) 

if len(word) >= 3:
    dict_word[word] += 1

#!/usr/bin/env python2
#coding: utf-8
import collections as C
count_word = C.Counter()
with open('input.txt', 'r') as f_in:
    for line in f_in.readlines():
        for word in line.split():
            if not len(word.decode('utf-8'))<3:
                count_word[word] += 1
                
print repr(count_word.most_common(10)).decode('string_escape')

[('что', 31), ('она', 26), ('Золушка', 21), ('только', 20), ('была', 18), ('сказала', 15), ('как', 14), ('так', 11), ('еще', 10), ('чем', 8)]

from collections import Counter
import re
Counter(map(str.lower, re.findall('\w{3}\w*', open('LICENSE').read()))).most_common(10)
Out[4]: 
[('the', 80),
 ('psf', 55),
 ('and', 47),
 ('python', 46),
 ('yes', 44),
 ('license', 37),
 ('any', 37),
 ('agreement', 32),
 ('this', 30),
 ('licensee', 29)]