计算每个键的出现次数

Question

我有以下用户

users = [
  { username: "user1", state: "USA" },
  { username: "user2", state: "Canada" },
  { username: "user3", state: "China" },
  { username: "user4", state: "China" },
  { username: "user4", state: "USA" },
];

我想计算每个状态出现的次数并打印它及其值。我的输出应该是这样的

USA, 2
Canada,1
China,2

我在 python 中使用了计数器，但遇到了问题。

users = [
  { username: "user1", state: "USA" },
  { username: "user2", state: "Canada" },
  { username: "user3", state: "China" },
  { username: "user4", state: "China" },
  { username: "user4", state: "USA" },
];
from collections import Counter

counts = Counter(c for c in 'users' if c in 'USA, Canada, China')
for k,v in counts.iteritems():
    print(k,v)

Answer 1

语法 { username: "user1", state: "USA" }, 仅在 javascript 中有效，在 python 中你也需要在键周围加上引号：{"username": "user1", "state": "USA" },

您还迭代了 'users'，这是一个字符串，您需要使用变量 users，然后使用 c['part']

获取状态部分

from collections import Counter

users = [
    {"username": "user1", "state": "USA"}, {"username": "user2", "state": "Canada"},
    {"username": "user3", "state": "China"}, {"username": "user4", "state": "China"},
    {"username": "user4", "state": "USA"},
]
counts = Counter(c['state'] for c in users)

for k, v in counts.items():
    print(k, v)

# iterate on descending count order
for k, v in counts.most_common():
    print(k, v)

计算每个键的出现次数

Counting occurence of each key

python

python-3.x

counter