python字典唯一值的计数

from collections import Counter
from itertools import chain

counts = Counter(chain.from_iterable(e.keys() for e in d))

这可确保正确计算输入列表中包含多个键的词典.

演示：

>>> from collections import Counter
>>> from itertools import chain
>>> d = [{"abc":"movies"},{"pqr":"sports"}]
>>> Counter(chain.from_iterable(e.keys() for e in d))
Counter({'pqr': 5,'abc': 3,'xyz': 1})

或输入词典中的多个键：

>>> d = [{"abc":"movies",'xyz': 'music','pqr': 'music'},{"abc": "sports",'pqr': 'movies'},{"abc": "music",'pqr': 'sports'},'xyz': 1})

Counter()具有其他有用的功能,例如.most_common() method以反向排序顺序列出元素及其计数：

for key,count in counts.most_common():
    print '{}: {}'.format(key,count)

# prints
# 5: pqr
# 3: abc
# 1: xyz