python - 访问 python 字典元素时遇到问题

Question

我有以下字典:

b = {None: u'{"TimeStamp":"2017-01-30T13:50:22.3854765+00:00","RealEstate":          {"Id":"fa9ba4d0-3e69-46f0-9460-05d6b2ff1211","Name":"Building 1","Room":"Room     1","Device":{"Id":"fa9ba4d0-3e69-46f0-9460-08d6b2ff6408","Payload":{"Temperature":{"Unit":"C","Value":32.3},"Humidity":{"Unit":"%","Value":12},"Light":{"Unit":"lux","Value":154},"Motion":{"Unit":"Number of motion","Value":0},"Co2":null}}},"Message":null}'}

并且无法访问任何元素。尝试了 b['None']、b['u'] 和 b['TimeStamp']，它们都会生成:

ERROR: ..../sparkstream.py", line 24, in test
    c = b['u']

按键错误:'u'

有什么建议吗!？

Answer 1

你有一本只有一个键的字典，你可以通过b[None]访问它的值。该值又是一个字符串，而不是字典。为了获取字典，您必须使用 JSON 对其进行解码:

import json

b = {None: u'{"TimeStamp":"2017-01-30T13:50:22.3854765+00:00","RealEstate":          {"Id":"fa9ba4d0-3e69-46f0-9460-05d6b2ff1211","Name":"Building 1","Room":"Room     1","Device":{"Id":"fa9ba4d0-3e69-46f0-9460-08d6b2ff6408","Payload":{"Temperature":{"Unit":"C","Value":32.3},"Humidity":{"Unit":"%","Value":12},"Light":{"Unit":"lux","Value":154},"Motion":{"Unit":"Number of motion","Value":0},"Co2":null}}},"Message":null}'}
dict_object = json.loads(b[None])
print json.dumps(dict_object, indent=2)  # Show the decoded result

# Accessing some keys
print '---'
print 'Time stamp:', dict_object['TimeStamp']
print 'Real Estate ID:', dict_object['RealEstate']['Id']
print 'Device ID:', dict_object['RealEstate']['Device']['Id']

输出:

{
  "TimeStamp": "2017-01-30T13:50:22.3854765+00:00", 
  "Message": null, 
  "RealEstate": {
    "Device": {
      "Id": "fa9ba4d0-3e69-46f0-9460-08d6b2ff6408", 
      "Payload": {
        "Motion": {
          "Value": 0, 
          "Unit": "Number of motion"
        }, 
        "Light": {
          "Value": 154, 
          "Unit": "lux"
        }, 
        "Co2": null, 
        "Temperature": {
          "Value": 32.3, 
          "Unit": "C"
        }, 
        "Humidity": {
          "Value": 12, 
          "Unit": "%"
        }
      }
    }, 
    "Room": "Room     1", 
    "Id": "fa9ba4d0-3e69-46f0-9460-05d6b2ff1211", 
    "Name": "Building 1"
  }
}
---
Time stamp: 2017-01-30T13:50:22.3854765+00:00
Real Estate ID: fa9ba4d0-3e69-46f0-9460-05d6b2ff1211
Device ID: fa9ba4d0-3e69-46f0-9460-08d6b2ff6408