Python 计算每个键的出现次数

我有以下用户作为

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，并将其与值一起打印。 我的输出应该是

USA, 2
Canada,1
China,2

我在python中使用了计数器，但我面临一些问题

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)

---

语法

{username:“user1”，state:“USA”}，

仅在

javascript

中有效，在python中，您还需要在键周围加引号：

{“username”：“user1”，“state”：“USA”}，

---

您还可以迭代

'users'

，这是一个字符串，您需要使用变量

users

，然后使用

c['part']

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)

---

语法

{username:“user1”，state:“USA”}，

仅在

javascript

中有效，在python中，您还需要在键周围加引号：

{“username”：“user1”，“state”：“USA”}，

---

您还可以迭代

'users'

，这是一个字符串，您需要使用变量

users

，然后使用

c['part']

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)

---

你面临什么问题？你面临什么问题？你不会去看医生然后说“我感觉不舒服”吧？请阅读，未定义的名称“username”是错误

。iteritems（）

是python 2.7函数。它已重命名为

.items（）

@12944qwerty谢谢您的帮助您面临哪些问题？您面临哪些问题？你不会去看医生然后说“我感觉不舒服”吧？请阅读，未定义的名称“username”是错误

。iteritems（）

是python 2.7函数。它已重命名为

.items（）

@12944qwerty谢谢您的帮助