Sort a dictionary by key in Python

This post will discuss how to sort a dictionary by its key in Python.

1. Using dictionary constructor

With Python 3.7 or CPython 3.6+, the dictionary order is the same as the insertion order. Therefore, we can get a sorted list of key-value pairs by passing the dictionary to the sorted() function. We can then use the dictionary constructor to get a new dictionary with those key-value pairs. We can see this behavior below:

d = {'one': 1, 'two': 2, 'three': 3, 'four': 4}

sortedDict = dict(sorted(d.items()))

# {'four': 4, 'one': 1, 'three': 3, 'two': 2}

print(sortedDict)

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To sort it in reverse order, we can pass the reverse argument as True:

d = {'one': 1, 'two': 2, 'three': 3, 'four': 4}

sortedDict = dict(sorted(d.items(), reverse=True))

# {'two': 2, 'three': 3, 'one': 1, 'four': 4}

print(sortedDict)

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2. Using `collections.OrderedDict()` class

Since dictionaries were unordered in Python before version 3.7, we couldn’t store them in a way that preserved the ordering. However, we can get a sorted list of key-value pairs by passing the dictionary’s items to the sorted() function. Then we can insert the entries of the sorted dictionary into an OrderedDict, which is a subclass of the dict class that remembers the order of the items. For example:

import collections

d = {'one': 1, 'two': 2, 'three': 3, 'four': 4}

sortedDict = collections.OrderedDict(sorted(d.items()))

# OrderedDict([('four', 4), ('one', 1), ('three', 3), ('two', 2)])

print(sortedDict)

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3. Using `json.dumps()` function

Another option is to pass our dictionary to the json.dumps() function with the sort_keys argument as True. Note that this returns the string representation of a sorted dictionary. Here is how we can use this function:

import json

d = {'one': 1, 'two': 2, 'three': 3, 'four': 4}

# {"four": 4, "one": 1, "three": 3, "two": 2}

print(json.dumps(d, sort_keys=True))

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4. Using `pprint.pprint()` function

To print the sorted representation of a dictionary, we can use the pprint.pprint() function. It prints the dictionary in sorted key order. For example:

import pprint

d = {'one': 1, 'two': 2, 'three': 3, 'four': 4}

# {'four': 4, 'one': 1, 'three': 3, 'two': 2}

pprint.pprint(d)

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That’s all about sorting a dictionary by key in Python.

Also See:

Sort a dictionary by value in Python

Sort a dictionary by key in Python

1. Using dictionary constructor

2. Using collections.OrderedDict() class

3. Using json.dumps() function

4. Using pprint.pprint() function

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2. Using `collections.OrderedDict()` class

3. Using `json.dumps()` function

4. Using `pprint.pprint()` function