Python：有效计数字典列表中某个键的唯一值的数量

Question

必须有一个更好的方式来编写这个Python代码，我有一个人名单（人是词典），我试图找到这个数字某个特定键的唯一值（在这种情况下，密钥被称为国籍，我试图找到独特的民族数量的人员列表）：

no_of_nationalities = [] 
for p in people: 
    no_of_nationalities.append(p['Nationality']) 
print 'There are', len(set(no_of_nationalities)), 'nationalities in this list.' 

非常感谢

Answer 1

count = len(set(p['Nationality'] for p in people)) 
print 'There are' + str(count) + 'nationalities in this list.' 

Answer 2

更好的方法是直接从字典中构建set ionaries：

print len(set(p['Nationality'] for p in people)) 

Answer 3

len(set(x['Nationality'] for x in p)) 

Answer 4

有collections模块

import collections 
.... 
count = collections.Counter() 
for p in people: 
    count[p['Nationality']] += 1; 
print 'There are', len(count), 'nationalities in this list.' 

这样你可以指望各民族过。

print(count.most_common(16))#print 16 most frequent nationalities