python - 如何在字典中创建值出现的直方图？

Question

使用python 2.6：

我有一本字典，其中每个键都包含一个值列表。

我想查看字典中的所有值，并计算每个值在所有键中出现的次数。

我一直在看 itervalues() 或

for value in dictionary.values():

首先，还有 .count() 函数，但我需要返回一个直方图。

例如：

print dictionary

会回来

{'test' : ['spam', 'eggs', 'cheese', 'spam'], 'test2' : ['spam', 'cheese', 'goats']}

我想告诉我一些事情：

{'spam' : 3, 'eggs' : 1, 'cheese': 2, 'goats' : 1}

Answer 1

from collections import Counter

d = {'test' : ['spam', 'eggs', 'cheese', 'spam'], 'test2' : ['spam', 'cheese', 'goats']}
c = Counter(sum(d.values(), []))
# or c = Counter(x for a in d.values() for x in a)
print c.most_common()

## [('spam', 3), ('cheese', 2), ('eggs', 1), ('goats', 1)]

对于 python 2.6 使用这个配方。

Answer 2

遍历值列表，并通过一一递增将它们添加到新字典中。

# start with an empty output dictionary
out = {}

# iterate through the keys in the dictionary
for key in p:
   # iterate through the values in the sublist
   for val in p[key]:
      # check to see if we've seen this one before
      if not out.has_key(val):
         # if not, start it out at 0
         out[val] = 0

      # increment by one because we've seen it once more
      out[val] += 1

print out