Sort a Dictionary by Value in Python

Introduction

A dictionary in Python is a collection of key-value pairs, where each key is unique. Sometimes, you might want to sort these dictionaries based on their values rather than their keys. Sorting a dictionary by value can help you analyze data more effectively. 

This article will guide you through different methods to sort a dictionary by its values in Python, with simple examples and explanations.

Methods to Sort a Dictionary by Value

Using sorted() Function

The sorted() function can be used to sort a dictionary by its values. The sorted() function returns a sorted list of the specified iterable's items.

Syntax

sorted(iterable, key=None, reverse=False)

• iterable: The sequence to be sorted.
   
• key: A function that serves as a key for the sort comparison.
   
• reverse: A Boolean. If True, the sorted list is reversed.

Example

• Python

Python

# Define a dictionary

my_dict = {'apple': 10, 'banana': 5, 'cherry': 7}


# Sort the dictionary by value

sorted_dict = dict(sorted(my_dict.items(), key=lambda item: item[1]))

print("Sorted Dictionary:", sorted_dict)

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Output

Sorted Dictionary: {'banana': 5, 'cherry': 7, 'apple': 10}

In this example, the dictionary is sorted by its values in ascending order using a lambda function as the key.

Sorting in Ascending and Descending Order

You can sort a dictionary in both ascending and descending order.

Ascending Order

• Python

Python

# Sort the dictionary by value in ascending order

sorted_dict_asc = dict(sorted(my_dict.items(), key=lambda item: item[1]))

print("Ascending Order:", sorted_dict_asc)

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Output:

Ascending Order: {'banana': 5, 'cherry': 7, 'apple': 10}

Descending Order

• Python

Python

# Sort the dictionary by value in descending order

sorted_dict_desc = dict(sorted(my_dict.items(), key=lambda item: item[1], reverse=True))

print("Descending Order:", sorted_dict_desc)

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Output

Descending Order: {'apple': 10, 'cherry': 7, 'banana': 5}

In the descending order example, the reverse=True argument is added to sort the values in descending order.

Using For Loop

You can sort a dictionary by its values using a for loop by iterating over the dictionary and sorting the key-value pairs manually.

• Python

Python

# Define the dictionary
my_dict = {'apple': 10, 'orange': 5, 'banana': 20, 'grape': 15}

# Sort the dictionary by value using a for loop
sorted_dict = {}
for key in sorted(my_dict, key=my_dict.get):
    sorted_dict[key] = my_dict[key]

# Output the sorted dictionary
print("Sorted dictionary by value:", sorted_dict)

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Output

Sorted dictionary by value: {'orange': 5, 'apple': 10, 'grape': 15, 'banana': 20}

Using Bubble Sort

Bubble Sort is a simple sorting algorithm that repeatedly compares adjacent items and swaps them if they are in the wrong order. To sort a dictionary by value, we can implement Bubble Sort on its items.

• Python

Python

# Define the dictionary
my_dict = {'apple': 10, 'orange': 5, 'banana': 20, 'grape': 15}

# Convert dictionary to a list of tuples (key, value)
dict_items = list(my_dict.items())

# Bubble Sort by value
n = len(dict_items)
for i in range(n):
    for j in range(0, n-i-1):
        if dict_items[j][1] > dict_items[j+1][1]:
            dict_items[j], dict_items[j+1] = dict_items[j+1], dict_items[j]

# Convert the sorted list back to a dictionary
sorted_dict = dict(dict_items)

# Output the sorted dictionary
print("Sorted dictionary by value using Bubble Sort:", sorted_dict)

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Output

Sorted dictionary by value using Bubble Sort: {'orange': 5, 'apple': 10, 'grape': 15, 'banana': 20}

Using item getter from the operator Module

Another way to sort a dictionary by value is by using itemgetter from the operator module.

Syntax

operator.itemgetter(n)

Example

• Python

Python

from operator import itemgetter

# Define a dictionary

my_dict = {'apple': 10, 'banana': 5, 'cherry': 7}


# Sort the dictionary by value using itemgetter

sorted_dict = dict(sorted(my_dict.items(), key=itemgetter(1)))


print("Sorted Dictionary:", sorted_dict)

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Output

Sorted Dictionary: {'banana': 5, 'cherry': 7, 'apple': 10}

In this example, itemgetter(1) is used to sort the dictionary by its values.

Handling Ties in Values

When sorting by values, ties (identical values) may occur. The default behavior is to retain the original order of keys with identical values.

Example

• Python

Python

# Define a dictionary with ties

my_dict = {'apple': 10, 'banana': 5, 'cherry': 7, 'date': 7}

# Sort the dictionary by value

sorted_dict = dict(sorted(my_dict.items(), key=lambda item: item[1]))

print("Sorted Dictionary with Ties:", sorted_dict)

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Output

Sorted Dictionary with Ties: {'banana': 5, 'cherry': 7, 'date': 7, 'apple': 10}

Sorting Nested Dictionaries

Sometimes dictionaries contain other dictionaries as values. Sorting these can be a bit more complex but follows the same principles.

Example

• Python

Python

# Define a nested dictionary

nested_dict = {

    'fruits': {'apple': 10, 'banana': 5},

    'vegetables': {'carrot': 3, 'beetroot': 8}

}

# Sort the nested dictionary by value of the inner dictionary

sorted_nested_dict = {k: dict(sorted(v.items(), key=lambda item: item[1])) for k, v in nested_dict.items()}

print("Sorted Nested Dictionary:", sorted_nested_dict)

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Output

Sorted Nested Dictionary: {'fruits': {'banana': 5, 'apple': 10}, 'vegetables': {'carrot': 3, 'beetroot': 8}}