Finding a parent key from a dict given an intermediate key using python

Question

I have a dictionary that looks like this:

d = {'dev':
        {<dev1>:
             {'mod':
                 {<mod1>:
                     {'port': [1, 2, 3]
                            }
                  }
              }
         <dev2>:
             {'mod':
                 {<mod3>:
                       {'port': [] }
                 }
             }
       }
  }

I want to be able to write a function, such that if i provide a search object such as 'mod1', it provides me the parent key as 'dev1'.

I have searched all over and tried a bunch of things, but couldnt seem to get this to work. Any help will be appreciated!

I have tried the stuff mentioned at the link below:

Python--Finding Parent Keys for a specific value in a nested dictionary

Find a key in a python dictionary and return its parents

What did you try? You will have to manually walk the entire dictionary tree looking for your target key. Also, there is no guarantee that it will occur only once. — BrenBarn, Jul 24 '15 at 20:23
Edits show what I have tried. @BrenBarn I understand I have to walk the dict to get the target key. But is there any way to retrieve the parent key? I understand there will be duplicates. But is there a way to get a list of the ones that contain this key? — nsJHDM, Jul 24 '15 at 20:27
@MorganThrapp - They do not seem to work for the dict structure that I have. I do not get anything back when I tried them out. — nsJHDM, Jul 24 '15 at 20:28
@MorganThrapp - any suggestions on what I might need to tweak in those solutions I posted or how else I need to do this traversal? — nsJHDM, Jul 24 '15 at 20:32
@nsJHDM You need to show a real MCVE (http://stackoverflow.com/help/mcve). Then maybe we can tell you what's wrong with what you're doing. — CrazyCasta, Jul 24 '15 at 20:40

score 1 · Accepted Answer · answered Jul 24 '15 at 20:36

This should work:

def find_parent_keys(d, target_key, parent_key=None):
  for k, v in d.items():
    if k == target_key:
      yield parent_key
    if isinstance(v, dict):
      for res in find_parent_keys(v, target_key, k):
        yield res

Usage:

d = {
  'dev': {
    'dev1': {
      'mod': {
        'mod1': {'port': [1, 2, 3]},
      },
    },
    'dev2': {
      'mod': {
        'mod3': {'port': []},
      },
    },
  },
}

print list(find_parent_keys(d, 'mod'))
print list(find_parent_keys(d, 'dev'))

Output:

['dev2', 'dev1']
[None]

Thanks! looping through this and recursively calling this function should get me what I want! :) — nsJHDM, Jul 24 '15 at 20:52

Finding a parent key from a dict given an intermediate key using python

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