Python：有效计算字典列表中键的唯一值数

一定有更好的方法来编写Python代码，我有一个人员列表（人员是字典），我试图找到某个键的唯一值的数量（在这种情况下，该键称为National，我试图在人员列表中找到唯一国籍的数量）：

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非常感谢

一个更好的方法是直接从字典构建

集合

：

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

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

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有

集合

模块

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

这样你也可以计算每个国籍

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

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如果我读对了原文，

people

是词典的集合，而不是词典本身。

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

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