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In Python how do I sort a list of dictionaries by values of the dictionary?
Sorting Python dictionary based on nested dictionary values

I have dictionary of the form as mentioned below:

a_dict = { 'e': (1, 100), 'a': (2, 3) }

I am unable to sort it by the second element of the tuple. The resultant dictionary will appear as below:

a_dict = { 'a': (2, 3), 'e': (1, 100) }
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  • @Tichodroma: that's a list of dictionaries, this is just one dictionary, not in a list. Commented Aug 13, 2012 at 10:49

2 Answers 2

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Dictionaries can't be sorted as such, but you can sort their contents:

sorted(a_dict.items(), key=lambda (k, (v1, v2)): v2)
sorted(a_dict.items(), key=lambda item: item[1][1])    # Python 3

You can put the results into a collections.OrderedDict (since 2.7):

OrderedDict(sorted(a_dict.items(), key=lambda (k, (v1, v2)): v2))
OrderedDict(sorted(a_dict.items(), key=lambda item: item[1][1])    # Python 3
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1 Comment

The argument unpacking done in your lambda will only work in Python 2.x. In Python 3 you'll need to do key=lambda k, v : v[1].
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In your example you are using list of dictionaries. Sorting the dict by key:

mydict = {'carl':40,
          'alan':2,
          'bob':1,
          'danny':3}

for key in sorted(mydict.iterkeys()):
    print "%s: %s" % (key, mydict[key])

alan: 2
bob: 1
carl: 40
danny: 3

If you want to sort a dict by values, please see How do I sort a dictionary by value?

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2 Comments

What list of dictionaries are you referring to? The code in the question has a dictionary with tuples as values, and no lists at all.
Of course you're right. I made a stupid mistake.