Sort nested dictionary by value, and remainder by another value, in Python

python sorting dictionary python-2.5
user479870 picture user479870 · Nov 5, 2010 · Viewed 43.6k times · Source

Consider this dictionary format.

{'KEY1':{'name':'google','date':20100701,'downloads':0},
 'KEY2':{'name':'chrome','date':20071010,'downloads':0},
 'KEY3':{'name':'python','date':20100710,'downloads':100}}

I'd like the dictionary sorted by downloads first, and then all items with no downloads sorted by date. Obviously a dictionary cannot be sorted, I just need a sorted listed of keys I can iterate over. 

['KEY3','KEY1','KEY2']

I can already sort the list by either value using sorted, but how do I sort by second value too?

Answer

Amber picture Amber · Nov 5, 2010

Use the key argument for sorted(). It lets you specify a function that, given the actual item being sorted, returns a value that should be sorted by. If this value is a tuple, then it sorts like tuples sort - by the first value, and then by the second value.

sorted(your_list, key=lambda x: (your_dict[x]['downloads'], your_dict[x]['date']))

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