Get list of all sub-keys from a python dictionary

Question

I have some dictionaries(json output). I want to get the base element which can be a list of strings or a string. Currently I am doing it like this:-

folder="shared/"
files=os.listdir('shared')


for f in files:
    f=folder+f
    print(f)
    with open(f) as f:
        data = json.load(f)
    #data is a dict now with sub-keys
    for key,value in data.items():
        if value.keys():
            print(value)
    break

This is the input dictionary that was read by the python code:-

{
  "shortshirt": {
    "ralphlauren": {
      "classic": [
        "That Ralph Lauren classic fit is a timeless look!",
        "Nice choice. Can’t go wrong with Ralph Lauren"
      ]
    }
  },
  "socks": {
    "": {
      "": ["Have to find the right socks to keep your feet cozy"]
    }
  }
}

And this is the output that I am getting:-

{'ralphlauren': {'classic': ['That Ralph Lauren classic fit is a timeless look!', 'Nice choice. Can’t go wrong with Ralph Lauren']}}
{'': {'': ['Have to find the right socks to keep your feet cozy']}}

But this is what I want:-

keys=[["shortshirt","ralphlauren","classic"],["socks"]]

value=[['That Ralph Lauren classic fit is a timeless look!', 'Nice choice. Can’t go wrong with Ralph Lauren'], ['Have to find the right socks to keep your feet cozy']]

But I don't know whether to have 2 or 3 level nested loops. If I have an inner loop and in actual there was no nested key then I get the value error. I want to get all the nested keys in a separate list and the base value or values like on the lowest level in another list, any help regarding this will be highly appreciated.

Your description is unclear. Provide the corresponding **expected** output for your sample data. — meowgoesthedog, Mar 19 '19 at 11:23
Well, this is because you are not going down the dictionary, so you are only getting the top-level values (that are dicts). For what you want you have to go down the dictionary until the value is not a dict. You could do it recursively. Same thing for the keys, and don't forget to filter the empty ones. — Javier Paz Sedano, Mar 19 '19 at 11:49
if I go down (add a loop) then how do I know how much deep should I go? Like I mean, I am going to write the code first, if I write 3 loops and the actual has 5 sub-keys, how will I get those? — Asim, Mar 19 '19 at 12:06
recursion, as @JavierPazSedano mentioned, then it would not matter how many sub-keys exist — gold_cy, Mar 19 '19 at 12:41

score 4 · Accepted Answer · answered Mar 19 '19 at 12:43

Generators are useful for this problem. Strategies –

Keys: keep track of the current recursion path. Yield the current path as soon as you hit a leaf.
Values: only yield leaves.

Code:

def getitems(obj):

  def getkeys(obj, stack):
    for k, v in obj.items():
      k2 = ([k] if k else []) + stack # don't return empty keys
      if v and isinstance(v, dict):
        for c in getkeys(v, k2):
          yield c
      else: # leaf
        yield k2

  def getvalues(obj):
    for v in obj.values():
      if not v: continue
      if isinstance(v, dict):
        for c in getvalues(v):
          yield c
      else: # leaf
        yield v if isinstance(v, list) else [v]

  return list(getkeys(obj,[])), list(getvalues(obj))

Input:

{
  "shortshirt": {
    "ralphlauren": {
      "classic": [
        "That Ralph Lauren classic fit is a timeless look!",
        "Nice choice. Can't go wrong with Ralph Lauren"
      ]
    }
  },
  "socks": {
    "": {
      "": ["Have to find the right socks to keep your feet cozy"]
    }
  }
}

Output:

# keys
[['classic', 'ralphlauren', 'shortshirt'], ['socks']]

# values
[['That Ralph Lauren classic fit is a timeless look!', "Nice choice. Can't go wrong with Ralph Lauren"], ['Have to find the right socks to keep your feet cozy']]

Get list of all sub-keys from a python dictionary

1 Answers1