There may be situations while working with dictionaries in python where we need to create a new dictionary from another dictionary by including some items from the dictionary based on a condition or we want to create a new dictionary having keys and values following a specific condition. We may do it by manually checking the dictionary items one by one using a for loop and adding them to the new dictionary. In this tutorial, we will see how we can achieve the same result using a concise construct called dictionary comprehension in python.<\/p>\n
Also Read: Java Program to Print Stair Case Number Pattern<\/a><\/p>\n Just like list comprehension is a way to create lists from other lists, dictionary comprehension is a way to create a python dictionary from another dictionary or from any other iterable. We can create new dictionaries with the same elements as the original dictionary based on conditional statements or we can transform the items in the dictionary according to our needs. We can either modify the keys or the values or both key and value of items in the dictionary while creating a new dictionary using dictionary comprehension.<\/p>\n While creating a dictionary using dictionary comprehension, we have to get a key-value pair either from any dictionary or from any other iterable.Syntax for dictionary comprehension can be as follows.<\/p>\n While creating a dictionary from a list or tuple using the elements of list or tuple as keys and values derived from the elements, we can use the following syntax.<\/p>\n While creating a dictionary from another dictionary, we can use the following syntax.<\/p>\n We can create a dictionary by using elements from a list. Suppose we want to create a\u00a0python dictionary\u00a0with elements of the list as keys and values then we can do it as follows.<\/p>\n Output:<\/p>\n In the output, we can see that the created dictionary has keys and values same as that of elements in the given list.<\/p>\n We can also modify the elements of the list before adding them to dictionary while creating a new dictionary. Suppose we want to create a dictionary having elements of the list as keys and their squares as values the we can do it as follows.<\/p>\n Output:<\/p>\n In the output, we can see that the created dictionary has elements of the list as keys and their squares as values.<\/p>\n We can also selectively use items from lists based on conditions while creating the dictionary. Suppose we want to create a dictionary having elements of the list which are even as keys and their squares as values the we can do it as follows.<\/p>\n Output:<\/p>\n In the output, we can see that only those elements of the list which are even numbers has been used as keys in the created dictionary and their squares are the respective values of the keys of the dictionary.<\/p>\n We can also create a dictionary\u00a0 by using items from another dictionary. For this we can extract key value pairs using\u00a0 For example, we can create a new dictionary exactly as a given dictionary using dictionary comprehension as follows.<\/p>\n Output:<\/p>\n In the output, we can see that the new dictionary is containing the same key value pairs as original dictionary.<\/p>\n We can also modify the dictionary items from the original dictionary before including them to the new dictionary.\u00a0For example, the following program modifies the values of the items before adding them into new dictionary.<\/p>\n Output:<\/p>\n In the output, we can see that the keys of the new dictionary as same as original dictionary but the values of the items in new dictionary as squares of values of the item in the original dictionary.<\/p>\n We can also use conditions to selectively choose items from the older dictionary using conditions\u00a0 while creating a new dictionary.<\/p>\n For example, the following program filters out the items whose keys are odd numbers and considers only those items to add in new dictionary in which the keys are even numbers. It further squares the values of those items before adding them to new dictionary.<\/p>\n Output:<\/p>\n In the output, we can see that the key value pairs in new dictionary have only even numbers as their keys and their squares as respective values.<\/p>\n In this article, we have seen what dictionary comprehension is and how to use them to create new dictionaries. Dictionary comprehensions can be used to replace for loops while creating dictionaries and make the source code more concise\u00a0 and increase the readability of the code when complex conditions are not used. In cases when we use complex conditional statements inside dictionary comprehension, it may decrease the readability of the source code. The execution of the code may also slow down and the program will require more memory space. So, while handling complex conditional statements to create dictionaries, it is better to use for loops instead of dictionary comprehensions. Stay tuned for more informative articles.<\/p>\n<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":" There may be situations while working with dictionaries in python where we need to create a new dictionary from another dictionary by including some items from the dictionary based on a condition or we want to create a new dictionary having keys and values following a specific condition. We may do it by manually checking…<\/p>\n","protected":false},"author":1,"featured_media":3991,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","footnotes":""},"categories":[2],"tags":[],"jetpack_featured_media_url":"https:\/\/pythonarray.com\/wp-content\/uploads\/2021\/07\/Dictionary-Comprehension-in-Python.png","jetpack-related-posts":[{"id":2402,"url":"https:\/\/pythonarray.com\/ways-to-create-dictionary-in-python\/","url_meta":{"origin":2373,"position":0},"title":"Ways to create dictionary in Python","date":"July 7, 2022","format":false,"excerpt":"In python, a dictionary is a data structure in which we can keep data in the form of key-value pairs. In this article, we will study and implement various methods to create a dictionary in python. Create an empty dictionary in python We can create an empty\u00a0python dictionary using curly\u2026","rel":"","context":"In "Python"","img":{"alt_text":"Ways to create dictionary in Python","src":"https:\/\/i2.wp.com\/pythonarray.com\/wp-content\/uploads\/2021\/07\/Ways-to-create-dictionary-in-Python.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":1380,"url":"https:\/\/pythonarray.com\/convert-dictionary-values-list-python\/","url_meta":{"origin":2373,"position":1},"title":"Convert Dictionary Values List Python | How to Convert Dictionary Values to a List in Python","date":"June 22, 2022","format":false,"excerpt":"Python programming learners can collect complete information about converting dictionary values to a list in python from this tutorial. Make use of this Convert Dictionary Values List Python Tutorial and acquire how values of the dictionary can convert into a list using a python programming language with Examples. Before going\u2026","rel":"","context":"In "Python"","img":{"alt_text":"Convert Dictionary Values List Python","src":"https:\/\/i2.wp.com\/pythonarray.com\/wp-content\/uploads\/2021\/06\/Convert-Dictionary-Values-List-Python.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":2385,"url":"https:\/\/pythonarray.com\/python-dictionary-basic-usage\/","url_meta":{"origin":2373,"position":2},"title":"Python Dictionary Basic Usage","date":"July 7, 2022","format":false,"excerpt":"Dictionary is another data type in Python. Python Programming - Dictionaries Dictionary Comprehension in Python Python Programming \u2013 Dictionary Functions and Methods Dictionary Overview A dictionary maps a set of key to a set of values. Dictionaries in Python are also known as hash tables. It requires that the keys\u2026","rel":"","context":"In "Python"","img":{"alt_text":"Python Dictionary Basic Usage","src":"https:\/\/i2.wp.com\/pythonarray.com\/wp-content\/uploads\/2021\/07\/Python-Dictionary-Basic-Usage.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":2390,"url":"https:\/\/pythonarray.com\/what-is-a-dictionary\/","url_meta":{"origin":2373,"position":3},"title":"What is a Dictionary","date":"July 7, 2022","format":false,"excerpt":"What is a Dictionary? Dictionaries are collections of items that have a \u201ckey\u201d and a \u201cvalue\u201d. Dictionaries are mutable. You do not have to reassign the dictionary to make changes to it. They are just like lists, except instead of having an assigned index number, you make up the index:\u2026","rel":"","context":"In "Python"","img":{"alt_text":"What is a Dictionary","src":"https:\/\/i1.wp.com\/pythonarray.com\/wp-content\/uploads\/2021\/07\/What-is-a-Dictionary.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":2377,"url":"https:\/\/pythonarray.com\/get-key-from-value-in-dictionary\/","url_meta":{"origin":2373,"position":4},"title":"Get key from value in dictionary","date":"December 2, 2022","format":false,"excerpt":"In Python, we can get the values present in a dictionary using the keys by simply using the syntax dict_name[key_name]. But there isn\u2019t any method to extract a key associated with the value when we have values. In this article, we will see the ways with help of which we\u2026","rel":"","context":"In "Python"","img":{"alt_text":"Get key from value in dictionary","src":"https:\/\/i1.wp.com\/pythonarray.com\/wp-content\/uploads\/2021\/07\/Get-key-from-value-in-dictionary.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]},{"id":2368,"url":"https:\/\/pythonarray.com\/copy-dictionary-in-python\/","url_meta":{"origin":2373,"position":5},"title":"Copy Dictionary in Python","date":"July 7, 2022","format":false,"excerpt":"While programming, there may be situations where we need to make an exact copy of a dictionary. In this article, we will look at different approaches to copy a dictionary in python and will implement those approaches. Copy dictionary using for loop We can create a copy of a python\u2026","rel":"","context":"In "Python"","img":{"alt_text":"Copy Dictionary in Python","src":"https:\/\/i0.wp.com\/pythonarray.com\/wp-content\/uploads\/2021\/07\/Copy-Dictionary-in-Python.png?resize=350%2C200&ssl=1","width":350,"height":200},"classes":[]}],"_links":{"self":[{"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/posts\/2373"}],"collection":[{"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/comments?post=2373"}],"version-history":[{"count":3,"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/posts\/2373\/revisions"}],"predecessor-version":[{"id":4317,"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/posts\/2373\/revisions\/4317"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/media\/3991"}],"wp:attachment":[{"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/media?parent=2373"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/categories?post=2373"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/pythonarray.com\/wp-json\/wp\/v2\/tags?post=2373"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}What is dictionary comprehension?<\/h3>\n
\n
myDict={key:value for var in iterable}<\/pre>\nmyDict={key:value for var in list_name}\r\nmyDict={key:value for var in tuple_name}<\/pre>\nmyDict={key:value for (key,value) in dict_name.items()}<\/pre>\nHow to use dictionary comprehension?<\/h3>\n
myList=[1,2,3,4]\r\nmyDict={x:x for x in myList}\r\nprint(\"List is:\")\r\nprint(myList)\r\nprint(\"Created dictionary is:\")\r\nprint(myDict)<\/pre>\nList is:\r\n[1, 2, 3, 4]\r\nCreated dictionary is:\r\n{1: 1, 2: 2, 3: 3, 4: 4}<\/pre>\nmyList=[1,2,3,4]\r\nmyDict={x:x**2 for x in myList}\r\nprint(\"List is:\")\r\nprint(myList)\r\nprint(\"Created dictionary is:\")\r\nprint(myDict)<\/pre>\nList is:\r\n[1, 2, 3, 4]\r\nCreated dictionary is:\r\n{1: 1, 2: 4, 3: 9, 4: 16}<\/pre>\nmyList=[1,2,3,4]\r\nmyDict={x:x**2 for x in myList if x%2==0}\r\nprint(\"List is:\")\r\nprint(myList)\r\nprint(\"Created dictionary is:\")\r\nprint(myDict)<\/pre>\nList is:\r\n[1, 2, 3, 4]\r\nCreated dictionary is:\r\n{2: 4, 4: 16}<\/pre>\nitems()<\/code>\u00a0method from the original dictionary.\u00a0items()\u00a0<\/code>method gives a list of tuples as\u00a0(key,value)<\/code> pairs which we can use to create a new dictionary.<\/p>\nmyDict={1:1,2:2,3:3,4:4}\r\nprint(\"Original Dictionary is\")\r\nprint(myDict)\r\nnewDict={key:value for (key,value) in myDict.items()}\r\nprint(\"New dictionary is:\")\r\nprint(newDict)<\/pre>\nOriginal Dictionary is\r\n{1: 1, 2: 2, 3: 3, 4: 4}\r\nNew dictionary is:\r\n{1: 1, 2: 2, 3: 3, 4: 4}<\/pre>\nmyDict={1:1,2:2,3:3,4:4}\r\nprint(\"Original Dictionary is\")\r\nprint(myDict)\r\nnewDict={key:value**2 for (key,value) in myDict.items()}\r\nprint(\"New dictionary is:\")\r\nprint(newDict)<\/pre>\nOriginal Dictionary is\r\n{1: 1, 2: 2, 3: 3, 4: 4}\r\nNew dictionary is:\r\n{1: 1, 2: 4, 3: 9, 4: 16}<\/pre>\nmyDict={1:1,2:2,3:3,4:4}\r\nprint(\"Original Dictionary is\")\r\nprint(myDict)\r\nnewDict={key:value**2 for (key,value) in myDict.items() if key%2==0}\r\nprint(\"New dictionary is:\")\r\nprint(newDict)<\/pre>\nOriginal Dictionary is\r\n{1: 1, 2: 2, 3: 3, 4: 4}\r\nNew dictionary is:\r\n{2: 4, 4: 16}<\/pre>\nConclusion<\/h3>\n