How can I sort a dictionary by key?

Question

What would be a nice way to go from {2:3, 1:89, 4:5, 3:0} to {1:89, 2:3, 3:0, 4:5}?
I checked some posts but they all use the "sorted" operator that returns tuples.

Answer 1

If you have a dict, for example:

not_ordered_dict = {5 : "5555", 9 : "9999", 1 : "1111"}

ordered_dict = {}

for key in sorted(not_ordered_dict):
    ordered_dict[key] = not_ordered_dict[key]   

Answer 2

Dictionaries themselves do not have ordered items as such, should you want to print them etc to some order, here are some examples:

In Python 2.4 and above:

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

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

gives:

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

(Python below 2.4:)

keylist = mydict.keys()
keylist.sort()
for key in keylist:
    print "%s: %s" % (key, mydict[key])

Source: http://www.saltycrane.com/blog/2007/09/how-to-sort-python-dictionary-by-keys/

Answer 3

I think the easiest thing is to sort the dict by key and save the sorted key:value pair in a new dict.

dict1 = {'renault': 3, 'ford':4, 'volvo': 1, 'toyota': 2} 
dict2 = {}                  # create an empty dict to store the sorted values
for key in sorted(dict1.keys()):
    if not key in dict2:    # Depending on the goal, this line may not be neccessary
        dict2[key] = dict1[key]

To make it clearer:

dict1 = {'renault': 3, 'ford':4, 'volvo': 1, 'toyota': 2} 
dict2 = {}                  # create an empty dict to store the sorted     values
for key in sorted(dict1.keys()):
    if not key in dict2:    # Depending on the goal, this line may not be  neccessary
        value = dict1[key]
        dict2[key] = value

Answer 4

For python3.6+, this is easily done with:

>>> d = {2:3, 1:89, 4:5, 3:0}
>>> dict(sorted(d.items()))
{1: 89, 2: 3, 3: 0, 4: 5}

Answer 5

As others have mentioned, dictionaries are inherently unordered. However, if the issue is merely displaying dictionaries in an ordered fashion, you can override the __str__ method in a dictionary subclass, and use this dictionary class rather than the builtin dict. Eg.

class SortedDisplayDict(dict):
   def __str__(self):
       return "{" + ", ".join("%r: %r" % (key, self[key]) for key in sorted(self)) + "}"


>>> d = SortedDisplayDict({2:3, 1:89, 4:5, 3:0})
>>> d
{1: 89, 2: 3, 3: 0, 4: 5}

Note, this changes nothing about how the keys are stored, the order they will come back when you iterate over them etc, just how they're displayed with print or at the python console.

Answer 6

I come up with single line dict sorting.

>> a = {2:3, 1:89, 4:5, 3:0}
>> c = {i:a[i] for i in dict.fromkeys(sorted([i for i in a]))}
>> print(c)
{1: 89, 2: 3, 3: 0, 4: 5}
[Finished in 0.4s]

Hope this will be helpful.