My_dict = {'2007': {'4': feat11,

                                '2': feat12,

                                    ...,

                                '1': feat1m},

                  '2005': {'3': feat21,

                               '2': feat22,

                                    ...,

                               '5': feat2n},

                  ......,

                 '2008': {'6' featN1,

                              '3': featN2,

                                    ...,

                              '7': featNk}

         }

Now, I want sort My_dict based on the external keys and internal keys. The codes are as follows:

import collections

My_dict = collections.OrderedDict(sorted(My_dict.itmes(), key=lambda tup=tup[0]))

for exter_id in My_dict.keys():

   exter_value = My_dict[exter_id]

   exter_value = collections.OrderedDict(sorted(exter_value.items(), key=lambda, tup=tup[0]))

   My_dict[exter_id] = exter_value   # don't forget

Referrence:

https://docs.python.org/3/howto/sorting.html#sortinghowto

https://docs.python.org/2/library/collections.html?highlight=ordereddict#collections.OrderedDict