Programs

Sort Dictionary by Value Python

Python is a popular programming language that can be used to create web applications on a server. It can be used to develop workflows alongside the software. In addition to connecting database systems, Python can also read and manipulate files. The programs can be devised to perform complex problems of mathematics and handle big data. It enables a production-ready development of software and quick prototyping. 

There are several primitive data types in Python, such as a dictionary, set, list, tuple etc. This popular programming language also encompasses collections modules with dedicated data structures such as deque, ChainMap etc.  These data types contain functions that make the Python code more efficient and hence it is easy for the user to work with them. The dictionary data type in Python has one such predefined function called the sort function. Let us discuss the sorting of the Python dictionary by values. 

Basics of Python Data Types:

The categorization or classification of data items in Python is referred to as data types. Several built-in data types are offered by Python. The Python built-in data types are mentioned below.

  1. Scalar Data Type

Examples: int, float, bool, complex, none

  1. Sequence data type

Examples: String, List and tuple

  1. Mapping data type

Examples: Dictionary

  1. Set data type

Examples: Set and frozenset

  1. Mutable and immutable data types

Numbers, tuples and strings are immutable, whereas lists of dictionary objects are mutable.

Dictionary in Python:

A collection data type in Python that consists of pairs of key and value similar to a map in other programming languages such as Java is called the dictionary data type. Some of the important features of the dictionary data type are listed below.

  • The data in a Dictionary can be altered even after the declaration of the dictionary in Python. Hence, Python Dictionary is mutable. 
  • The keys in a Dictionary are distinct. However, the values permit duplicate entries. Also, the Python dictionary is unordered. 
  • The keys are used as indexes to access the values in a dictionary.
  • A dictionary in Python is declared within a pair of curly brackets. 

Several operations that can be used in a Python dictionary are as follows.

  • copy
  • clear
  • get
  • fromkeys
  • items
  • popitem
  • keys
  • pop
  • setdefault
  • values
  • update

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Why is Sorting a dictionary in Python required?

  • Unlike a list with the search time complexity of O(n), the search time complexity of a dictionary is O(1). Hence, the dictionary can be used as a feasible action wherever required.
  • A sorted dictionary offers better clarity and understanding in executing the operations.
  • An effective analysis of any data structure is enabled by sorting a dictionary in Python.

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Different Methods of Sorting a Dictionary:

Sorting of a dictionary in Python can be accomplished through various methods, as listed below.

  • Sorting by keys
  • Sort dictionary by values
  • Custom sorting algorithms using string and number 
  • Reverse the sorted order

Sorting dictionaries by values in Python can be accomplished through various approaches. 

  • for Loop approach
  • Use sorted () function
  • Use operated Module and itemgetter()
  • Sort using Lambda function
  • Return a new dictionary with sorted values

Let us discuss all these approaches in detail in the subsequent sections.

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Sorting Dictionary Using a for Loop:

A for Loop can be used to sort a dictionary by value in Python. The values of the dictionary are ordered with the sorted() function. The compiler then loops through the sorted values to determine the keys for each value. The key-value pairs are sorted in the same order to form a new dictionary. The dictionary cannot be reordered after sorting since the order pairs are written in an entirely new dictionary.

 

 

Sort dictionary with sorted() function:

The sorted() function is used to sort the array values. While sorting a dictionary, the sorted() function accepts one or more parameter in the following syntax.

sorted(dict1, key=dict1.get)

In the above code statement, the ‘key’ is the function that is invoked on each element before comparing the values for sorting. The value for a key in the dictionary is returned by the get() method on the objects of the dictionary. The expression “sorted(dict1, key=dict1.get)” will revert a key’s list for which the values are sorted in a specified order. A new dictionary that is sorted can be created with this.

 

The sorted() function reduces the code size. When combined with the itemgetter() function, the sorted() function provides a more concise solution to sort a dictionary by value in Python. 

Use operator Module and itemgetter() to sort dictionary:

The itemgetter() function is included in the module ‘operator’. This function reverts a callable object that can return an element from an object. A callable object that reverts any dictionary value with ‘2’ as its key is created with the itemgetter() function in the example below.

 

The items() method can be accessed by every dictionary. The key-value pairs are returned as a list of tuples by this method. The itemgetter() method can be used to sort the tuples’ list by pulling the tuple’s second value. Once the tuples list is sorted, a new dictionary can be created with those values.

 

Use of Lambda functions to sort Dictionary in Python:

The nameless or anonymous functions in Python are referred to as the Lambda functions. The use of the lambda function eliminates the need of importing the 

The methods discussed till now are compatible only with Python 3.7 and other higher versions. However, the next method that will be discussed is compatible with the earlier versions too. 

A new dictionary is returned with Sorted Values:

The collections module contains the OrderedDict() function that can be used to retain the sorted dictionary. This can be used once the dictionary is sorted by values. 

 

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