python - 如何避免 Python 中的双循环？

Question

来自 https://jsonplaceholder.typicode.com/todos 处的数据我想按用户计算“已完成”的项目。

目前，我通过首先收集现有的用户 ID 键来解决这个问题，然后为数据集中的每个元素检查它是否为当前用户所有，并将其附加到该用户的项目列表中。

users_items = {}

import json
from urllib import request

# Data from
uri = "https://jsonplaceholder.typicode.com/todos"

response = request.urlopen(uri).read()
data = json.loads(response)

def get_user_ids(items):
    for item in items:
        users_items[item['userId']] = None

def get_user_items():
    for uid in users_items:
        items = []
        for item in data:
            if(item['userId'] == uid):
                items.append(item['completed'])
        users_items[uid] = items

done_items_by_user = {}
def count_completed_by_user():
    for user in users_items:
        done_items_by_user[user] = sum(users_items[user])

get_user_ids(data)
get_user_items()

我特别不喜欢 get_users_ids 中的双循环和用空列表初始化字典值。

Answer 1

只需 defaultdict对象:

import json
from urllib import request
from collections import defaultdict

# Data from
uri = "https://jsonplaceholder.typicode.com/todos"

response = request.urlopen(uri).read()
data = json.loads(response)


def count_user_completed_items(data):
    result = defaultdict(int)
    for item in data:
        if item['completed']: result[item['userId']] += 1
    return dict(result)


print(count_user_completed_items(data))

输出(其中键是“用户 ID”，值是一些“完成”项):

{1: 11, 2: 8, 3: 7, 4: 6, 5: 12, 6: 6, 7: 9, 8: 11, 9: 8, 10: 12}