You just need a simple .keys()
>>> dct = {
...     "1": "a",
...     "3": "b",
...     "8": {
...         "12": "c",
...         "25": "d"
...     }
... }
>>>
>>> dct.keys()
['1', '8', '3']
>>> for key in dct.keys(): print key
...
1
8
3
>>>
If you need a sorted list:
keylist = dct.keys()
keylist.sort()
Hope it helps!!
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Thanks!