python nested lists/dictionaries and popping values

Question

Apologies in advance for this being such a newbie question. I'm just beginning to write python and i've been having some confusion around popping values from nested dictionaries/lists so i appreciate any help!

I have this sample json data:

{ "scans": [
   { "status": "completed", "starttime": "20150803T000000", "id":533},
   { "status": "completed", "starttime": "20150803T000000", "id":539}
] }

i'd like to pop the 'id' out of the "scans" key.

def listscans():
  response = requests.get(scansurl + "scans", headers=headers, verify=False)
  json_data = json.loads(response.text)
  print json.dumps(json_data['scans']['id'], indent=2)

doesnt seem to be working because the nested key/values are inside of a list. i.e.

>>> print json.dumps(json_data['scans']['id'])
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: list indices must be integers, not str

can anyone point me in the right direction to get this to work? my longterm goal with this is to create a for-loop that places all of the id's into another dictionary or list that i can use for another function.

Answer 1

json_data['scans'] returns a list of dicts, you are trying to index the list using a str i.e []["id"] which fails for obvious reasons so you need to use the index to get each subelement:

print json_data['scans'][0]['id'] # -> first dict
print json_data['scans'][1]['id'] # -> second dict

Or to see all the id's iterate over the list of dicts returned using json_data["scans"]:

for dct in json_data["scans"]:
    print(dct["id"]) 

To save append to a list:

all_ids = []
for dct in json_data["scans"]:
    all_ids.append(dct["id"])

Or use a list comp:

all_ids = [dct["id"] for dct in json_data["scans"]]

If there is a chance the key id might not be in every dict, use in to check before you access:

all_ids = [dct["id"] for dct in json_data["scans"] if "id" in dct]