当没有任何返回时处理 JSON 解码错误

我正在解析 json 数据。我没有解析的问题，我使用的是 simplejson模块。但是一些 api 请求返回空值。下面是我的例子:

{
"all" : {
"count" : 0,
"questions" : [     ]
}
}

这是我解析 json 对象的代码片段:

 qByUser = byUsrUrlObj.read()
qUserData = json.loads(qByUser).decode('utf-8')
questionSubjs = qUserData["all"]["questions"]

正如我在一些请求中提到的，我得到以下错误:

Traceback (most recent call last):
File "YahooQueryData.py", line 164, in <module>
qUserData = json.loads(qByUser)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/simplejson/__init__.py", line 385, in loads
return _default_decoder.decode(s)
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/simplejson/decoder.py", line 402, in decode
obj, end = self.raw_decode(s, idx=_w(s, 0).end())
File "/opt/local/Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages/simplejson/decoder.py", line 420, in raw_decode
raise JSONDecodeError("No JSON object could be decoded", s, idx)
simplejson.decoder.JSONDecodeError: No JSON object could be decoded: line 1 column 0 (char 0)

处理此错误的最佳方法是什么？

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小开
最佳答案

There is a rule in Python programming called "it is Easier to Ask for Forgiveness than for Permission" (in short: EAFP). It means that you should catch exceptions instead of checking values for validity.

Thus, try the following:

try:
qByUser = byUsrUrlObj.read()
qUserData = json.loads(qByUser).decode('utf-8')
questionSubjs = qUserData["all"]["questions"]
except ValueError:  # includes simplejson.decoder.JSONDecodeError
print('Decoding JSON has failed')

EDIT: Since simplejson.decoder.JSONDecodeError actually inherits from ValueError (proof here), I simplified the catch statement by just using ValueError.

小开

If you don't mind importing the json module, then the best way to handle it is through json.JSONDecodeError (or json.decoder.JSONDecodeError as they are the same) as using default errors like ValueError could catch also other exceptions not necessarily connected to the json decode one.

from json.decoder import JSONDecodeError




try:
qByUser = byUsrUrlObj.read()
qUserData = json.loads(qByUser).decode('utf-8')
questionSubjs = qUserData["all"]["questions"]
except JSONDecodeError as e:
# do whatever you want

//EDIT (Oct 2020):

As @Jacob Lee noted in the comment, there could be the basic common TypeError raised when the JSON object is not a str, bytes, or bytearray. Your question is about JSONDecodeError, but still it is worth mentioning here as a note; to handle also this situation, but differentiate between different issues, the following could be used:

from json.decoder import JSONDecodeError




try:
qByUser = byUsrUrlObj.read()
qUserData = json.loads(qByUser).decode('utf-8')
questionSubjs = qUserData["all"]["questions"]
except JSONDecodeError as e:
# do whatever you want
except TypeError as e:
# do whatever you want in this case

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