How To Sort A Dictionary By Value In Python

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In Python, dictionaries are unordered collections of key-value pairs. Although dictionaries themselves cannot be sorted, we can extract their keys and values, sort them according to their values, and display the sorted key-value pairs in various ways. In this blog post, we will explore how to sort a dictionary by value in Python using different techniques and examples.

Using the sorted() Function and Lambda

One common approach to sort a dictionary by value is to use the built-in sorted() function along with a lambda function as the key. The sorted() function takes an iterable (e.g., a list, tuple, or dictionary) as input and returns a sorted list.

The lambda function helps to specify the sorting criteria. In our case, we want to sort the dictionary according to its values. Here’s an example:

# Sample dictionary
sample_dict = {‘apple’: 5, ‘orange’: 3, ‘banana’: 8, ‘grape’: 1}

# Sort dictionary by value
sorted_dict = sorted(sample_dict.items(), key=lambda x: x[1])

print(sorted_dict)

In this example, sample_dict.items() returns a view object displaying a list of the dictionary’s key-value tuple pairs. The key=lambda x: x[1] parameter in the sorted() function sorts these items based on their values (i.e., x[1] in the lambda function).

The output of the sorted dictionary will be: 

        [('grape', 1), ('orange', 3), ('apple', 5), ('banana', 8)]

Sorting in Descending Order

If you want to sort the dictionary by value in descending order, you can add reverse=True as an argument in the sorted() function. Here’s an example:

# Sort dictionary by value in descending order
sorted_dict_desc = sorted(sample_dict.items(), key=lambda x: x[1], reverse=True)

print(sorted_dict_desc)

The output will be: 

        [('banana', 8), ('apple', 5), ('orange', 3), ('grape', 1)]

Using the operator Module

Another way to sort a dictionary by value is to use the operator module. The module has a function called itemgetter() that can replace the lambda function as the key in the sorted() function. Here’s an example:

import operator

# Sort dictionary by value
sorted_dict_operator = sorted(sample_dict.items(), key=operator.itemgetter(1))

print(sorted_dict_operator)

The output will be the same as in the first example: 

        [('grape', 1), ('orange', 3), ('apple', 5), ('banana', 8)]

Conclusion

In this post, we have explored different techniques to sort a dictionary by value in Python. While using the sorted() function with a lambda function or the operator.itemgetter() function are the most common methods, it’s essential to choose the approach that best suits your needs and coding preferences.