Richard Richard - 5 months ago 26
JSON Question

python JSON to dict check if single or multiple children

I am using python2.7 and receive dynamically a JSON string that I need to parse.

The resulting dict looks as follows"

{
u'queueId': u'channel.presence'
u'name': u'presence.message'
u'timestamp': 1467756404358
u'webhookId': u'U3P3Xw'
u'serial': u'e7da73f968767379:37'
u'data': {

u'channelId': u'private-cc-259970d91ab44af38393130e95de7057'
u'site': u'eu-central-1-A'
u'presence': {

u'action': u'enter'
u'connectionId': u'LA84hfOd_w'
u'data': u'a012a914cce6096c4a02a29da51dbc58'
u'clientId': u'a012a914cce6096c4a02a29da51dbc58'
}
}
},
{
u'queueId': u'channel.presence'
u'name': u'presence.message'
u'timestamp': 1467756452665
u'webhookId': u'U3P3Xw'
u'serial': u'e7da73f968767379:40'
u'data': {

u'channelId': u'private-a012a914cce6096c4a02a29da51dbc58'
u'site': u'eu-central-1-A'
u'presence': [
{
u'timestamp': 1467756404550
u'connectionId': u'LA84hfOd_w'
u'clientId': u'a012a914cce6096c4a02a29da51dbc58'
u'action': 3
u'data': u'a012a914cce6096c4a02a29da51dbc58'
u'id': u'LA84hfOd_w-2:0'
}
]
}
},


As you can see from the example data the [data][presence] can have either just a single object or multiple objects.

My testing for that fails utterly with the exception:

Error: list indices must be integers, not str


My code:

for ji in json_data['items']:
channel_id = ji['data']['channelId']
logger.debug("ChannelID: %s" % channel_id)
found_special_case = False
if len(ji['data']['presence']) > 1 :
for ch in ji['data']['presence']:
...


Unfortunatly the check
len(ji['data']['presence']) > 1
is also true when there is only one item. In that case
ch
becomes 'action' instead of the child item.

How can I check whether there is a single or several items in a dictionary?

Answer

You can use isinstance() to determine if the item is a list or not:

presence = ji['data']['presence']
if isinstance(presence, list):
    # ...

Though, if I understand you correctly, this is the logic you are looking for:

presence = ji['data']['presence']
if isinstance(presence, dict):  # or: if not isinstance(presence, list):
    presence = [presence]

for ch in presence:
    # ...