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To: python-list@python.org
From: Gelonida N <gelonida@gmail.com>
Subject: Re: Get keys from a dicionary
Date: Fri, 11 Nov 2011 18:45:00 +0100
References: <8f5215a8-d08f-4355-a5a2-77fcaa32c92d@j10g2000vbe.googlegroups.com> <j9jm2n$gik$1@dough.gmane.org>
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Xref: x330-a1.tempe.blueboxinc.net comp.lang.python:15602

On 11/11/2011 02:31 PM, macm wrote:
> > Hi Folks
> >
> > I pass a nested dictionary to a function.
> >
> > def Dicty( dict[k1][k2] ):
> > 	print k1
> > 	print k2
> >
> > There is a fast way (trick) to get k1 and k2 as string.
> >
> > Whithout loop all dict. Just it!
> >
> > Regards
> >
> > macm


If my guessing was correct is this what you are looking for?


nesteddict = { 'a': { 'A' : 'value1 a_A' , 'B' : 'value2 a_B' },
               'b': { 'A' : 'value3 b_A' , 'B' : 'value4 b_B' },
               'c': { 'A' : 'value3 b_A' , 'B' : 'value4 b_B' },
             }

def find_in_nested_dict(adict, avalue):
    results = []
    for key1, sub_dict in adict.items():
        for key2, value in sub_dict.items():
            if avalue == value:
                results.append( (key1, key2) )
    return results

def mk_lookup(adict):
    lookup = {}
    for key1, sub_dict in adict.items():
        for key2, value in sub_dict.items():
            entry = lookup.get(value, [])
            entry.append( (key1, key2) )
            lookup[value] = entry
    return lookup

# good if you just want so search one value
value = nesteddict['c']['B']
keys =  find_in_nested_dict(nesteddict, value)
print "found %r in %r" % (value, keys)

# if you need many lookups perhaps better to 'precalculate a
# 'reversed' dict
lookup = mk_lookup(nesteddict)
keys =  lookup[value]
print "found %r in %r" % (value, keys)