Python嵌套列表解析，用于计算列表中相同字符串的出现次数

Question

I need to transform the following list:

[
  [u'starred', u'review'],
  [u'starred', u'review'],
  [u'starred', u'review', u'pinned'],
  [u'starred'],
  [u'starred'],
  [u'starred', u'review']
]

into the following dict

{
  u'starred': 6,
  u'review': 4,
  u'pinned': 1
}

I've got the feeling that it should be possible by using list comprehension or a generator expression, but I'm not sure though.

Any ideas?

Answer 1

How about

import itertools, collections
c = collections.Counter(itertools.chain(*your_list))

Answer 2

Flatten you list with generator expression and use collections.Counter :

from collections import Counter

Counter(x for sub in L for x in sub)