How To Sort A Dictionary By Value in Python?

Summary: Use one of the following methods to sort a dictionary by value:

  1. Using The sorted(dict1, key=dict1.get) Method.
  2. Using Dictionary Comprehension And Lambda With sorted() Method.
  3. Using OrderedDict (For Older Versions Of Python).
  4. Using itemgetter() with sorted() Method.
  5. Using Counter subclass.

Problem: Given a dictionary; how to sort it by values?

Example: The following example shows a dictionary by the name rank that stores the names of individuals as the keys while their corresponding ranks represent the values. We shall be using this example as a reference while discussing the solutions.

rank = {
  'Bob': 2,
  'Alice': 4,
  'Sharon': 5,
  'Dwyane': 1,
  'John': 3
}

# Some Procedure to Sort the Dictionary by its Values

Output:

{'Dwyane': 1, 'Bob': 2, 'John': 3, 'Alice': 4, 'Sharon': 5}

Before we dive into the solutions here are a few Points To Remember about dictionaries:

  • From Python 3.7 onwards, Python dictionaries are ordered (Insertion is also ordered). This means the ordered in which the keys are inserted into dictionaries are preserved.
  • In normal scenario sorting dictionaries, results in a sorted dictionary with respect to its keys.

To get a better insight into Python dictionaries, please follow our Blog Tutorial on dictionaries here. However, the purpose of this article is purely to guide you through the numerous methods to sort a dictionary based on the values instead of the keys. So without further delay let us dive into the solutions.

➤ Here’s a quick overview of all the methods used in this article. Please follow the slide show give below:

Method 1: Using The sorted(dict1, key=dict1.get) Method

The sorted() method is an in-built method in Python which is used to sort the elements of an iterable in a specific order (ascending or descending). After sorting the elements it returns the sorted sequence, in the form of a sorted list.

Syntax:

In order to sort the dictionary using the values, we can leverage the power of the sorted() function. To sort the dictionary based on the value, we can use the get() method and pass it to the key argument of the sorted() function.

Let us have a look at the following code to understand the usage of sorted function in order to solve our problem:

rank = {
  'Bob': 2,
  'Alice': 4,
  'Sharon': 5,
  'Dwyane': 1,
  'John': 3
}

for w in sorted(rank, key=rank.get):
    print(w, rank[w])

Output:

Dwyane 1
Bob 2
John 3
Alice 4
Sharon 5

In order to sort the dictionary using its values in reverse order, we need to specify the reverse argument as true, i.e.,

rank = {
  'Bob': 2,
  'Alice': 4,
  'Sharon': 5,
  'Dwyane': 1,
  'John': 3
}

for w in sorted(rank, key=rank.get, reverse=True):
    print(w, rank[w])

Output:

Sharon 5
Alice 4
John 3
Bob 2
Dwyane 1

Method 2: Using Dictionary Comprehension And Lambda With sorted() Method

If you are using Python 3.6 and above then our problem can be solved in a single line using a dictionary comprehension and a lambda function within the sorted method. This is an efficient and concise solution to sort dictionaries based on their values.

⦿ Dictionary Comprehension is a concise and memory-efficient way to create and initialize dictionaries in one line of Python code. It consists of two parts: expression and context. The expression defines how to map keys to values. The context loops over an iterable using a single-line for loop and defines which (key, value) pairs to include in the new dictionary. To learn more about dictionary comprehensions in python have a look at our blog tutorial here.

Now, let us have a look at the following code given below that explains the usage of dictionary comprehensions to solve our problem in a single lie of code.

rank = {
  'Bob': 2,
  'Alice': 4,
  'Sharon': 5,
  'Dwyane': 1,
  'John': 3
}

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

Output:

{'Dwyane': 1, 'Bob': 2, 'John': 3, 'Alice': 4, 'Sharon': 5}

Method 3: Using OrderedDict (For Older Versions Of Python)

Dictionaries are generally unordered for versions prior to Python 3.7, so it is not possible to sort a dictionary directly. Therefore, to overcome this constraint we need to use the OrderedDict subclass.

⦿ An OrderedDict is a dictionary subclass that preserves the order in which key-values are inserted in a dictionary. It is included in the collections module in Python.

Let us have a look at how we can use OrderedDict to order dictionaries in earlier versions of Python and sort them.

from collections import OrderedDict
rank = {
  'Bob': 2,
  'Alice': 4,
  'Sharon': 5,
  'Dwyane': 1,
  'John': 3
}
a = OrderedDict(sorted(rank.items(), key=lambda x: x[1]))
for key,value in a.items():
  print(key, value)

Output:

('Dwyane', 1)
('Bob', 2)
('John', 3)
('Alice', 4)
('Sharon', 5)

Method 4: Using itemgetter() With The sorted() Method

⦿ itemgetter() is a built-in function of the operator module that constructs a callable that accepts an iterable like a list, tuple, set, etc as input and fetches the nth element out of it.

Example:

from operator import itemgetter

rank = {
  'Bob': 2,
  'Alice': 4,
  'Sharon': 5,
  'Dwyane': 1,
  'John': 3
}

a = sorted(rank.items(), key=itemgetter(1))
print(dict(a))

Output:

{'Dwyane': 1, 'Bob': 2, 'John': 3, 'Alice': 4, 'Sharon': 5}

In the above example a stores a list of tuples. Therefore we converted it to a dictionary explicitly, while printing.

Method 5: Using Counter

Counter is a dictionary subclass that is used for counting hashable objects. Since the values we are using are integers, we can use the Counter class to sort them. The Counter class has to be imported from the collections module.

Disclaimer: This is a work-around for the problem at hand and might not fit in every situation. Since, values of the dictionary in our case are integers, the Counter subclass fits as a solution to our problem. Consider it as a bonus trick!😉

from collections import Counter

rank = {
  'Bob': 2,
  'Alice': 4,
  'Sharon': 5,
  'Dwyane': 1,
  'John': 3
}

count = dict(Counter(rank).most_common())
print(count)

Output:

{'Dwyane': 1, 'Bob': 2, 'John': 3, 'Alice': 4, 'Sharon': 5}

⦿ In the above program the method most_common() has been used to return all elements in the Counter.

Conclusion

In this we learned about the following methods to sort a dictionary by values in Python:

  • Using The sorted(dict1, key=dict1.get) Method.
  • Using Dictionary Comprehension And Lambda With sorted() Method.
  • Using OrderedDict (For Older Versions Of Python).
  • Using itemgetter() with sorted() Method.
  • Using Counter subclass.

I hope after reading this article you can sort dictionaries by their values with ease. Please subscribe and stay tuned for more interesting articles in the future.

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