how to parse json where key is variable in python?


i am parsing a log file which is in json format, and contains data in the form of key : value pair.

i was stuck at place where key itself is variable. please look at the attached code

in this code i am able to access keys like username,event_type,ip etc.

problem for me is to access the values inside the "submission" key where

<strong>i4x-IITB-CS101-problem-33e4aac93dc84f368c93b1d08fa984fc_2_1</strong> is a variable key which will change for different users,

how can i access it as a variable ?

{ "username": "batista", "event_type": "problem_check", "ip": "", "event": { "submission": { "i4x-IITB-CS101-problem-33e4aac93dc84f368c93b1d08fa984fc_2_1": { "input_type": "choicegroup", "question": "", "response_type": "multiplechoiceresponse", "answer": "MenuInflater.inflate()", "variant": "", "correct": true } }, "success": "correct", "grade": 1, "correct_map": { "i4x-IITB-CS101-problem-33e4aac93dc84f368c93b1d08fa984fc_2_1": { "hint": "", "hintmode": null, "correctness": "correct", "npoints": null, "msg": "", "queuestate": null } }

this is my code how i am solving it :

import json import pprint with open("log.log") as infile: # Loop until we have parsed all the lines. for line in infile: # Read lines until we find a complete object while (True): try: json_data = json.loads(line) username = json_data['username'] print "username :- " + username except ValueError: line += next(infile)

how can i access <strong>i4x-IITB-CS101-problem-33e4aac93dc84f368c93b1d08fa984fc_2_1</strong> key and

data inside this key ??


You don't need to know the key in advance, you can simply iterate over the dictionary:

for k,v in obj['event']['submission'].iteritems(): print(k,v)


Suppose you have a dictionary of type d = {"a":"b"} then d.popitem() would give you a tuple ("a","b") which is (key,value). So using this you can access key-value pairs without knowing the key.

In you case if j is the main dictionary then j["event"]["submission"].popitem() would give you tuple

("i4x-IITB-CS101-problem-33e4aac93dc84f368c93b1d08fa984fc_2_1": { "input_type": "choicegroup", "question": "", "response_type": "multiplechoiceresponse", "answer": "MenuInflater.inflate()", "variant": "", "correct": true })

Hope this is what you were asking.


using python json module you'll end up with a dictionary of parsed values from the above JSON data

import json parsed = json.loads(this_sample_data_in_question) # parsed is a dictionary, so are "correct_map" and "submission" dictionary keys within "event" key

So you could iterate over the key, values of the data as a normal dictionary, say like this:

for k, v in parsed.items(): print k, v

Now you could find the (possible different values) of "i4x-IITB-CS101-problem-33e4aac93dc84f368c93b1d08fa984fc_2_1" key in a quick way like this:

import json parsed = json.loads(the_data_in_question_as_string) event = parsed['event'] for key, val in event.items(): if key in ('correct_map', 'submission'): section = event[key] for possible_variable_key, its_value in section.items(): print possible_variable_key, its_value

Of course there might be better way of iterating over the dictionary, but that one you could choose based on your coding taste, or performance if you have a fairly larger kind of data than the one posted in here.


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