json parsing using dictionaries

Question

I have a json file that look like this: I will have to extract the events eg. 'APP_STARTED' 'ORIENTATION' etc

{u'ParamElement_ReceivedTime': u'2012-11-02-00-05-31-748', 
 u'ParamElement_Name': u'LOG_CONTENT', 
 u'ParamElement_Info_0': 
 {u'dict': 
 {u'Events_list': [
 {
 u'Event': u'APP_STARTED', 
 u'time': u'2012-11-01 20:00:59.565 -0400'}, 
 {
 u'time': u'2012-11-01 20:01:01.168 -0400', 
 u'Event': u'ORIENTATION', 
 u'Orientation': u'Portrait'}, 
 {u'Event': u'CLIENT_RESULT_RECEIVED', 
 u'time': u'2012-11-01 20:01:15.927 -0400'}, 
 {u'Prev_SessionID': u'802911CC329E47139B61B58E21BF2FFF', 
 u'Prev_TransactionID': u'2', 
 u'Tab_Index': u'5', 
 u'time': u'2012-11-01 20:01:15.941 -0400', 
 u'Event': u'RESOLVED_TAB', 
 u'Accuracy': u'5.000000'}, 
 {u'Prev_TransactionID': u'2', 
 u'Prev_SessionID': u'802911CC329E47139B61B58E21BF2FFF', 
 u'Event': u'CLIENT_RESULT_RECEIVED', 
 u'time': u'2012-11-01 20:01:16.568 -0400'}
 }

The whole thing is stored in a variable called event_dict. I have a code that looks like:

if event_dict:
 if 'dict' in event_dict['ParamElement_Info_0']:
 if 'el' in event_dict['ParamElement_Info_0']['dict']:
 if 'e' in event_dict['ParamElement_Info_0']['dict']['el']:
 print e['Event'] 

What could be the mistake?

• David Robinson: What mistake? What error or incorrect behavior are you getting?
• user1189851: no error. I tried to print dict and it is empty.

Answer 1

Python approach is Ask forgiveness, not permission, and it is easier and better to use try-catch blocks instead of condition checks unless condition fail must be handled separately.

try:
 event = event_dict['ParamElement_Info_0']['dict']['Events_list']
except Exception, e:
 log('Opsss, incorrect data format: %s' % e.message)

In that way, you can see your errors easily.

Answer 2

You never define the variable e: your last line should be a loop, not a conditional like the earlier lines:

for e in event_dict['ParamElement_Info_0']['dict']['el']:
 print e

Also, I think you say "el" when you would need to say "Events_list", making your corrected code:

if event_dict:
 if 'dict' in event_dict['ParamElement_Info_0']:
 if 'Events_list' in event_dict['ParamElement_Info_0']['dict']:
 for e in event_dict['ParamElement_Info_0']['dict']['Events_list']:
 print e

• user1189851: Yes i use el for Events_list
• David Robinson: What do you mean you "use el"? The name of the string in your dictionary is Events_list. You are checking whether that string is in your dictionary. You can't check for an entirely different string. Did you mean for it to be a for loop, like for el in event_dict...?
• user1189851: Sorry, I was meaning for el in event_dict... I did not change it back to event_list. Thanks for the pointer.
• user1189851: This prints 'Event' and its value.

Answer 3

There is no 'el' element in your dictionary. When you write a for A in B you are creating a variable A to hold the contents of the iterable B. What you are doing is saying, if the key 'el' is in my dictionary... which it isn't. But Events_list is as @David points out.

Here is what may be an easier approach.

def item_getter(struct, key):
 parts = key.split('.', 1)
 if len(parts) > 1:
 key_part, rest_part = parts
 return item_getter(struct.get(key_part, {}), rest_part)
 return struct.get(key, None)
items = item_getter(event_dict, "ParamElement_Info_0.dict.Events_list")
events = [item.get('Event', 'No Event') for item in items]
print events

OUTPUT

[u'APP_STARTED', u'ORIENTATION', u'CLIENT_RESULT_RECEIVED', u'RESOLVED_TAB', u'CLIENT_RESULT_RECEIVED']