I have a dictionary of unique keys where some keys share the same value.

For example:

D = {'ida':{'key':'1'},'idb':{'key':'2'},'idc':{'key':'3'},'idd':{'key':'3'},'ide':{'key':'4'},'idf':{'key':'4'},'idg':{'key':'4'}}

I want a list of keys that share the same value with other keys.

In this case, it would be

l = ['idc','idd','ide','idf','idg']

However, I want to exclude one key from all sets of keys that share the same value.

For example, I'd like to have the keys

l = ['idd','idf','idg']

which excludes 'idc' and 'ide'

or it could be

l = ['idc','ide','idf']

which excludes 'idd' and 'idg'.

If the value appears more than once the list comp will add the key.

dup_keys = [k for k in D if sum(D[k] in x for x in D.iteritems()) > 1 ]['idf', 'idg', 'idd', 'ide', 'idc']dup_keys[1:]
['idg', 'idd', 'ide', 'idc']
dup_keys[1:-1]
['idg', 'idd', 'ide']

if sum(D[k] in x for x in D.iteritems()) > 1 checks the value appears > 1 times.

To ignore certain keys add some and condition, I am not sure on what basis you want to ignore the keys.