列表中列表的计数器对象的总和

Question

I am trying to find the sum of occurrence of a words from a list in a multiple lists. the list objects within list is huge so I used just a dummy instance

multiple=[['apple','ball','cat']['apple','ball']['apple','cat'].......]
words=['apple','ball','cat','duck'......]
word = 'apple' 
cnt = Counter()
total = 0
for i in multiple:
        for j in i:
            if word in j:
                cnt[word] +=1
                total += cnt[word]

I wanted an output like this:

{'apple':3,'ball':2,'cat':2}

Answer 1

You can just feed the Counter a generator expression:

cnt = Counter(word for sublist in multiple for word in sublist)

cnt
Out[40]: Counter({'apple': 3, 'ball': 2, 'cat': 2})

sum(cnt.values())
Out[41]: 7

I didn't really see the point of your words list. You didn't use it.

If you need to filter out words that are not in words , make words a set , not a list .

words = {'apple','ball','cat','duck'}

cnt = Counter(word for sublist in multiple for word in sublist if word in words)

Otherwise you get O(n**2) behavior in what should be a O(n) operation.

Answer 2

This works in Python 2.7 and Python 3.x:

from collections import Counter

multiple=[['apple','ball','cat'],['apple','ball'],['apple','cat']]
words=['apple','ball','cat','duck']
cnt = Counter()
total = 0
for i in multiple:
        for word in i:
            if word in words:
                cnt[word] +=1
                total += 1
print cnt  #: Counter({'apple': 3, 'ball': 2, 'cat': 2})
print dict(cnt)  #: {'apple': 3, 'ball': 2, 'cat': 2}
print total  #: 7
print sum(cnt.values())  #: 7

In Python 2.x you should use .itervalues() instead of .values() even though both work.

A bit shorter solution, based on roippi's answer:

from collections import Counter
multiple=[['apple','ball','cat'],['apple','ball'],['apple','cat']]
cnt = Counter(word for sublist in multiple for word in sublist)
print cnt  #: Counter({'apple': 3, 'ball': 2, 'cat': 2})