CODEWITHSUNDEEP
python
Marjana
Marjana

Reputation: 11

Build a nested dictionary with a list

I am struggling with how to define a list and append to it while looping through parsed json doc. I can't append to the list that's not defined. But I don't want to set to empty list, as that would override values I had in it in next iteration. This is what I have:

from collections import defaultdict
nested_dict = lambda: defaultdict(nested_dict)
hash = nested_dict()
   for e in decoded_jason['volumeList']:
       volumeName = e['name']
       volumeType = e['volumeType']
       if volumeType == 'Snapshot':
          consistencyGroupId = e['consistencyGroupId']
          #I am missing a step here to initialize empty list so I can append
          hash['map']['consistencyGroup'][consistencyGroupId].append(volumeName)

if I do this before append, it works, but then the list will be set to empty in next iteration:

hash['map']['consistencyGroup'][consistencyGroupId]=[]
hash['map']['consistencyGroup'][consistencyGroupId].append(volumeName)

Upvotes: 1

Views: 61

Answers (1)

Donnie
Donnie

Reputation: 46923

Make your final line be:

hash['map']['consistencyGroup'].setdefault(consistencyGroupId, []).append(volumeName)

setdefault either returns the value for the key if it's present, or, if it's not, sets it to the provided default ([] in this case), and then returns that.

Upvotes: 2

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