Dictionary Comprehensions

List comprehensions and dictionary comprehensions are comparable, but dictionary comprehensions make building dictionaries simple. In dictionary comprehension, it is possible to create the value and the key in the same loop.

Dictionary comprehensions in Python are a concise way to create dictionaries using a single line of code. It is especially useful when you want to convert one kind of data into another.

Advantages of Dictionary Comprehensions

Concise and Readable: It replaces multiline for loops with a single-line
Avoid the need for explicit loops: By summarizing the logic of iterating through the iterable, implementing transformations, and creating key-value pairs in one concise line of code
Allows easy transformation of data structures

Syntax

Following is the syntax of dictionary comprehension which helps us to create a new dictionary in one line of code.

{key: value for item in iterable (if condition)}

Return value

It returns a new dictionary that is created by the dictionary comprehension.

Example

The following example creates a dictionary from a list in which the length of each element serves as the value and it becomes a key:

words = ["apple", "banana", "cherry"]
word_length = {word: len(word) for word in words}
print(word_length) # Output: {'apple': 5, 'banana': 6, 'cherry': 6}

Output

word_length is a new dictionary in which each word in the word list is assigned a key and a value based on its length.

Example

This example Create a dictionary where the key is the number and the value is its square:

numbers = [1, 2, 3, 4, 5]
# Create a dictionary where the key is the number and the value is its square
squares = {x: x ** 2 for x in numbers}
print(squares) # Output: {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}

Output

The above code generates this output which contains the key as the number and the value as its square., i.e. {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}.

Example

In the below example, we transform a dictionary:

original = {'a': 1, 'b': 2, 'c': 3}
transformed = {key: value*2 for key, value in original.items()}
print(transformed)

Output

{'a': 2, 'b': 4, 'c': 6}

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Beginner 5 Hours

Dictionary comprehensions in Python are a concise way to create dictionaries using a single line of code. It is especially useful when you want to convert one kind of data into another.

Advantages of Dictionary Comprehensions

Concise and Readable: It replaces multiline for loops with a single-line
Avoid the need for explicit loops: By summarizing the logic of iterating through the iterable, implementing transformations, and creating key-value pairs in one concise line of code
Allows easy transformation of data structures

Syntax

Following is the syntax of dictionary comprehension which helps us to create a new dictionary in one line of code.

python
{key: value for item in iterable (if condition)}

Return value

It returns a new dictionary that is created by the dictionary comprehension.

Example

The following example creates a dictionary from a list in which the length of each element serves as the value and it becomes a key:

python
words = ["apple", "banana", "cherry"]
word_length = {word: len(word) for word in words}
print(word_length) # Output: {'apple': 5, 'banana': 6, 'cherry': 6}

Output

word_length is a new dictionary in which each word in the word list is assigned a key and a value based on its length.

Example

This example Create a dictionary where the key is the number and the value is its square:

python
numbers = [1, 2, 3, 4, 5]
# Create a dictionary where the key is the number and the value is its square
squares = {x: x ** 2 for x in numbers}
print(squares) # Output: {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}

Output

The above code generates this output which contains the key as the number and the value as its square., i.e. {1: 1, 2: 4, 3: 9, 4: 16, 5: 25}.

Example

In the below example, we transform a dictionary:

python
original = {'a': 1, 'b': 2, 'c': 3}
transformed = {key: value*2 for key, value in original.items()}
print(transformed)

Output

{'a': 2, 'b': 4, 'c': 6}

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Frequently Asked Questions for Python

What is Python programming used for?

Python is commonly used for developing websites and software, task automation, data analysis, and data visualisation. Since it's relatively easy to learn, Python has been adopted by many non-programmers, such as accountants and scientists, for a variety of everyday tasks, like organising finances.

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Python's syntax is a lot closer to English and so it is easier to read and write, making it the simplest type of code to learn how to write and develop with. The readability of C++ code is weak in comparison and it is known as being a language that is a lot harder to get to grips with.

Which is better Java or Python?

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The point is that Java is more complicated to learn than Python. It doesn't matter the order. You will have to do some things in Java that you don't in Python. The general programming skills you learn from using either language will transfer to another.

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Read on for tips on how to maximize your learning. In general, it takes around two to six months to learn the fundamentals of Python. But you can learn enough to write your first short program in a matter of minutes. Developing mastery of Python's vast array of libraries can take months or years.

How to learn Python quickly?

6 Top Tips for Learning Python

Choose Your Focus. Python is a versatile language with a wide range of applications, from web development and data analysis to machine learning and artificial intelligence.
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How to practice Python on a laptop?

The following is a step-by-step guide for beginners interested in learning Python using Windows.

Set up your development environment.
Install Python.
Install Visual Studio Code.
Install Git (optional)
Hello World tutorial for some Python basics.
Hello World tutorial for using Python with VS Code.

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Best YouTube Channels to Learn Python

Corey Schafer.
sentdex.
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Python can be written on any computer or device that has a Python interpreter installed, including desktop computers, servers, tablets, and even smartphones. However, a laptop or desktop computer is often the most convenient and efficient option for coding due to its larger screen, keyboard, and mouse.

Which code to learn first?

Write your first Python programStart by writing a simple Python program, such as a classic "Hello, World!" script. This process will help you understand the syntax and structure of Python code.

Where to study Python?

Google's Python Class.
Microsoft's Introduction to Python Course.
Introduction to Python Programming by Udemy.
Learn Python - Full Course for Beginners by freeCodeCamp.
Learn Python 3 From Scratch by Educative.
Python for Everybody by Coursera.
Learn Python 2 by Codecademy.

How to start Python for beginners?

Understand why you're learning Python. Firstly, it's important to figure out your motivations for wanting to learn Python.
Get started with the Python basics.
Master intermediate Python concepts.
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Build a portfolio of projects.
Keep challenging yourself.

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Top 5 Python Certifications - Best of 2024

PCEP (Certified Entry-level Python Programmer)
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