Handle JSON Decode Error when nothing returned

Question

I am parsing json data. I don't have an issue with parsing and I am using simplejson module. But some api requests returns empty value. Here is my example:

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

This is the segment of my code where I parse the json object:

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

As I mentioned for some requests I get the following error:

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) 

What would be the best way to handle this error?

Answer 1

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.