Generate Dictionary From List As Keys

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List Comprehension is a handy and faster way to create lists in Python in just a single line of code. It helps us write easy to read for loops in a single line.

  1. Generate Dictionary From List As Keys List
  2. Python Create Dict With Keys From List
  3. Generate Dictionary From List As Keys In Spanish
Generate dictionary from list as keys list

In Python, dictionary is a data structure to store data such that each element of the stored data is associated with a key. Dictionary data structure lets you query the data using key very efficiently.

The idea of comprehension is not just unique to lists in Python. Dictionaries, one of the commonly used data structures in data science, can also do comprehension. With dict comprehension or dictionary comprehension, one can easily create dictionaries.

A is the list, 0 is the default value. Pay attention not to set the default value to some mutable object (i.e. List or dict), because it will be one object used as value for every key in the dictionary (check here for a solution for this case). Numbers/strings are safe. The following code takes a dictionary of lists (indexed by keyword) and converts it into a list of list of dictionaries that contains all possible permutations of those lists. However, my solution. Second Iteration x will be 2: for 2 in range(1, 6) myDictx = 2. 2 = 2. Do the Same for the remaining iterations. Program to Create Dictionary of keys from 1 to n and values are square of keys Example 2. How to create Python dictionary from list of keys and values? Python Server Side Programming Programming If L1 and L2 are list objects containing keys and respective values, following methods can be used to construct dictionary object.

Remember that, in python a list is defined with square brackets [] and a dictionary is defined with curly braces {}. The idea used in list comprehension is carried over in defining dict comprehension as well. Dict comprehension is defined with a similar syntax, but with a key:value pair in expression.

In Python, you can have a List of Dictionaries. You already know that elements of the Python List could be objects of any type. In this tutorial, we will learn how to create a list of dictionaries, how to access them, how to append a dictionary to list and how to modify them. Mar 30, 2012  Dictionaries are the fundamental data structure in Python, and a key tool in any Python programmer's arsenal. They allow O(1) lookup speed, and have been heavily optimized for memory overhead and lookup speed efficiency. Today I'm going to show you three ways of constructing a Python dictionary, as well as some additional tips and tricks.

  • {key:value for i in list}

Let’s create a dictionary from this list with list elements as keys and values as integers from 0 to n-1 (n is size of list) i.e. Python ' Converting a list to dictionary with list elements as values in dictionary and keys are enumerated index starting from 0 i.e. Index position of element in list ' dictOfWords = i: listOfStri for i.

Let us see 5 simple examples of using Dict Comprehension to create new dictionaries easily.

[update:] Added sixth example of dict comprehension to delete keys in a dictionary.

Dict Comprehension Example 1

Let us see a quick example of creating a dict comprehension from a list of numbers.

Here let us use a list of numbers and create a dictionary with string value of the number as key and the number as values.

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Dict Comprehension Example 2

Let us say, we have a list of fruits and we can use dict comprehension to create a dictionary with fruits, the list elements as the keys and the length of each string as the values.

Dict Comprehension Example 3

Let us create a dictionary with dict comprehension such that elements of the list as the keys and the elements with first letter capitalized as the values.

Dict Comprehension Example 4

Let us use enumerate function in dictionary comprehension. If you have not used enumerate: enumerate can take any thing iterable as input and returns element and its index.

Here we use enumerate function on the list to create index and list element tuples and use them to create a dictionary with dict comprehension. We create a dictionary with elements of the list as the keys and the index of elements as the values. Such dictionaries with element index are often useful in a variety of scenarios.

Dict Comprehension Example 5

Another use of dict comprehension is to reverse key:value in an existing dictionary. Sometimes you may want to create new dictionary from an existing directory, such that the role of key:value pair in the first dictionary is reversed in the new dictionary. We can use Dict Comprehension and flip the element to index dictionary to index to element dictionary.

We have used dictionaries’ items function to get key, value pairs in an existing dictionary and created a new dictionary where the keys in the original dictionary are values in new dictionary and vice versa.

List

Generate Dictionary From List As Keys List


Dict Comprehension Example 6: How To Delete Selected Keys from Dictionary using Dict Comprehension?

Let us say you have dictionary and want to create a new dictionary by removing certain key-value pair. We can use Dict Comprehension to remove selected key-value pairs from a dictionary and create a new dictionary.

Let us use the “fruit” dictionary we created above.

Let us use diction comprehension to remove two keys, apple and banana, and their values from the fruit dictionary.

We have removed the keys, apple and cherry, by simply using dict keys object with set operations and now the new dictionary contains just banana and mango.

Python Create Dict With Keys From List

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Generate Dictionary From List As Keys In Spanish

VB.NET program that benchmarks Dictionary and ListModule Module1 Sub Main() ' Create Dictionary and List. Dim lookup As Dictionary(Of String, Integer) = New Dictionary(Of String, Integer) For i As Integer = 0 To 1000 lookup.Add(i.ToString(), 1) Next Dim list As List(Of String) = New List(Of String) For i As Integer = 0 To 1000 list.Add(i.ToString()) Next Dim m As Integer = 1000 ' Version 1: search Dictionary. Dim s1 As Stopwatch = Stopwatch.StartNew For i As Integer = 0 To m - 1 If Not lookup.ContainsKey('900') Then Return End If Next s1.Stop() Dim s2 As Stopwatch = Stopwatch.StartNew ' Version 2: search List. For i As Integer = 0 To m - 1 If Not list.Contains('900') Then Return End If Next s2.Stop() Dim u As Integer = 1000000 Console.WriteLine(((s1.Elapsed.TotalMilliseconds * u) / m).ToString('0.00 ns')) Console.WriteLine(((s2.Elapsed.TotalMilliseconds * u) / m).ToString('0.00 ns')) End SubEnd ModuleOutput 35.10 ns Dictionary ContainsKey (1000 keys)6801.10 ns List Contains (1000 elements)