如何在 Python 中正确错误检查 JSON 值？

Question

好的，我有这段代码，我从 instagram 的 api 获取一些 json ......

      instaINFO = requests.get("https://api.instagram.com/v1/media/%s?access_token=xyz" % instaMeID).json()
      print instaINFO
      #pdb.set_trace()
      MSG = {'fromEMAIL': uEmail, 'toCHANNELID': channelID, 'timeSENT': uTi    me, 'profilePIC': instaINFO['data']['user']['profile_picture'],'userNAME': instaINFO[    'data']['user']['username'], 'msgBODY': instaINFO['data']['caption']['text']}

但有时

       instaINFO['data']['caption']['text'] 

可能没有任何数据。 我把这个拿回来了。

      MSG = {'fromEMAIL': uEmail, 'toCHANNELID': channelID, 'timeSENT': uTime,
      'profilePIC': instaINFO['data']['user']['profile_picture'],'userNAME':
      instaINFO['data']['user']['username'], 'msgBODY': instaINFO['data']['caption']
      ['text']}
      TypeError: 'NoneType' object is not subscriptable

错误检查或防御性编码不是我的专长... 那么如果json值=无，我如何让代码通过

我尝试过这样做，但无济于事......

      if instaINFO['data']['caption']['text'] == None:
       pass

Answer 1

如果你想尽可能地填充MSG字典，你需要分别添加每个值：

MSG = {'fromEMAIL': uEmail, 'toCHANNELID': channelID, 'timeSENT': uTime}
try:
    MSG['profilePIC'] = instaINFO['data']['user']['profile_picture']
except TypeError:
    MSG['profilePIC'] = ""
try:
    MSG['userNAME'] = instaINFO['data']['user']['username']
except TypeError:
    MSG['userNAME'] = ""
try:
    MSG['msgBODY'] = instaINFO['data']['caption']['text']
except TypeError:
    MSG['msgBODY'] = ""

或者，为了避免违反 DRY 原则：

MSG = {'fromEMAIL': uEmail, 'toCHANNELID': channelID, 'timeSENT': uTime}
for mkey, subdict, ikey in (('profilePIC', 'user', 'profile_picture'), 
                            ('userNAME', 'user', 'username'),
                            ('msgBODY', 'cpation', 'text')):
    try:
        MSG[msgkey] = instaINFO['data'][subdict][instakey]
    except TypeError:
        MSG[msgkey] = ""