How to sort a dictionary in Python by values?

Python allows dictionaries to be sorted using the built-in sorted() function. In this article, we will explore different ways to sort a dictionary in Python by its values.

Using itemgetter() Method

The itemgetter() method from the operator module provides an efficient way to sort dictionaries by values. It returns a callable object that fetches an item from its operand using the provided index ?

from operator import itemgetter

dictionary = {
    'b': 2,
    'a': 1,
    'd': 4,
    'c': 3
}

# Sorting by values using itemgetter
sorted_dict = dict(sorted(dictionary.items(), key=itemgetter(1)))
print(sorted_dict)

{'a': 1, 'b': 2, 'c': 3, 'd': 4}

Using Lambda Function

A lambda function provides a concise way to sort dictionaries by values. The lambda expression accesses the value part of each key-value pair ?

dictionary = {
    'b': 2,
    'a': 1,
    'd': 4,
    'c': 3
}

# Sorting dictionary by values using lambda
sorted_dict = dict(sorted(dictionary.items(), key=lambda item: item[1]))
print(sorted_dict)

{'a': 1, 'b': 2, 'c': 3, 'd': 4}

Sorting in Descending Order

To sort dictionary values in descending order, add the reverse=True parameter to the sorted() function ?

dictionary = {
    'b': 2,
    'a': 1,
    'd': 4,
    'c': 3
}

# Sorting in descending order
sorted_dict = dict(sorted(dictionary.items(), key=lambda item: item[1], reverse=True))
print(sorted_dict)

{'d': 4, 'c': 3, 'b': 2, 'a': 1}

Using OrderedDict

The OrderedDict from the collections module was useful in Python versions before 3.7 to maintain insertion order. Modern Python dictionaries maintain order by default ?

from collections import OrderedDict

dictionary = {
    'b': 2,
    'a': 1,
    'd': 4,
    'c': 3
}

# Using OrderedDict (mainly for compatibility)
sorted_dict = OrderedDict(sorted(dictionary.items(), key=lambda item: item[1]))
print(sorted_dict)
print(type(sorted_dict))

OrderedDict([('a', 1), ('b', 2), ('c', 3), ('d', 4)])
<class 'collections.OrderedDict'>

Comparison of Methods

Conclusion

Use lambda functions for readable code in most cases. Choose itemgetter() for better performance with large datasets. Modern Python dictionaries maintain order automatically, making OrderedDict less necessary.