python 字典比较

问题描述

问 题

一个列表当中有一个日期的值，我想求这个日期里面当天最大时间的那一条，大神们如何写呢？
原始列表
`

    [{
    "count": 0,
    "create_time": "2017-03-22 22:00:00",
    "level": "1"
  },
  {
    "count": 5,
    "create_time": "2017-03-22 22:00:00",
    "level": "0"
  },
  {
    "count": 5,
    "create_time": "2017-03-22 22:00:00",
    "level": "2"
  },
  {
    "count": 5,
    "create_time": "2017-03-22 23:00:00",
    "level": "0"
  },
  {
    "count": 0,
    "create_time": "2017-03-22 23:00:00",
    "level": "1"
  },
  {
    "count": 5,
    "create_time": "2017-03-22 23:00:00",
    "level": "2"
  }]`
  

想要输出的列表

[{
        "count": 5,
        "create_time": "2017-03-22 23:00:00",
        "level": "0"
      },
      {
        "count": 0,
        "create_time": "2017-03-22 23:00:00",
        "level": "1"
      },
      {
        "count": 5,
        "create_time": "2017-03-22 23:00:00",
        "level": "2"
      }]

解决方案

在上次问的问题里改sum成max:

from collections import defaultdict
grouped = defaultdict(list)

for d in s:
    grouped[(d['create_time'].split()[0], d['level'])].append((d['create_time'], d['count']))
summed = {k : max(grouped[k]) for k in grouped}
s = [{'count': summed[k][1], 'create_time': summed[k][0], 'level': k[1]} for k in summed]

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