用Python从JSON中提取特定值

Question

我在Python中有一个JSON对象，它来自调用一个API (使用urllib2)的结果，如下所示：

results = urllib2.urlopen(req).read()
json1 = json.loads(results)

这将生成一个JSON对象，该对象包含类似的内容(由于大小而被截断)：

"http://d.opencalais.com/dochash-1/895ba8ff-4c32-3ae1-9615-9a9a9a1bcb39/cat/1":{
    "_typeGroup":"topics",
    "category":"http://d.opencalais.com/cat/Calais/Entertainment_Culture",
    "classifierName":"Calais",
    "categoryName":"Entertainment_Culture",
    "score":1
},
"http://d.opencalais.com/genericHasher-1/b6a2d07d-133b-35ad-85e2-54d524e750cf":{
    "_typeGroup":"entities",
    "_type":"TVShow",
    "name":"Hard Knocks",
    "_typeReference":"http://s.opencalais.com/1/type/em/e/TVShow",
    "instances":[
          {
          "detection":"[ New York Jets during the summer of 2010 on HBO's ]Hard Knocks[.\n]",
          "prefix":" New York Jets during the summer of 2010 on HBO's ",
          "exact":"Hard Knocks",
          "suffix":".\n",
          "offset":135,
          "length":11
          }
    ],
    "relevance":0.5
},

"http://d.opencalais.com/genericHasher-1/802a1ebb-7fac-354f-b02f-6ef8442950d3":{
    "_typeGroup":"entities",
    "_type":"Organization",
    "name":"New York Jets",
    "organizationtype":"sports",
    "nationality":"American",
    "_typeReference":"http://s.opencalais.com/1/type/em/e/Organization",
    "instances":[
          {
          "detection":"[ Tebow caught a few training camp glimpses of the ]New York Jets[ during the summer of 2010 on HBO's Hard]",
          "prefix":" Tebow caught a few training camp glimpses of the ",
          "exact":"New York Jets",
          "suffix":" during the summer of 2010 on HBO's Hard",
          "offset":86,
          "length":13
          }
    ],
    "relevance":0.5
}

从这个JSON，我想提取"_type“和”名称“，只有当"typeGroup”==“实体”。

例如，对于上面的JSON对象，输出应该如下所示：

TVShow: Hard Knocks
Organization: New York Jets.

有谁能帮忙用Python来做这件事吗？

更新1

根据贾丁的回答，我尝试了以下几点：

for key,value in json1.items():
    if value["_typeGroup"] == "entities":
        print value['_type'], value['name']

但是，这会导致错误KeyError：'_typeGroup‘

我试图了解键和值是如何按以下方式打印的：

for key,value in json1.items():
    print key,value

这导致了以下输出(只显示一个键，值对)：

http://d.opencalais.com/genericHasher-1/802a1ebb-7fac-354f-b02f-6ef8442950d3 {u'_typeReference': u'http://s.opencalais.com/1/type/em/e/Organization', u'_type': u'Organization', u'name': u'New York Jets', u'_typeGroup': u'entities', u'instances': [{u'suffix': u" during the summer of 2010 on HBO's Hard", u'prefix': u' Tebow caught a few training camp glimpses of the ', u'detection': u"[ Tebow caught a few training camp glimpses of the ]New York Jets[ during the summer of 2010 on HBO's Hard]", u'length': 13, u'offset': 86, u'exact': u'New York Jets'}], u'relevance': 0.5, u'nationality': u'American', u'organizationtype': u'sports'}

它似乎是一个嵌套的JSON。因此，我尝试了如下方法来访问内部键值对：

for key,value in json1.items():
    val1 = value
    for key,value in val1.items():
        if value["_typeGroup"] == "entities":
            print value['_type'], value['name']

但是，它会引发以下错误：

TypeError: string indices must be integers

Answer 1

我认为您得到了这个错误，因为您的JSON中的一些值没有_typeGroup。试试这个：

for key,value in x.items():
    if value.get("_typeGroup", "") == "entities":
        print value['_type'], value['name']

Answer 2

for key,value in json1.items():
    if value.get('typeGroup') == "entities":
        print value.get('_type'), value.get('name')

试试这个让我知道。应该管用的。