Do you find yourself interested in learning Python dictionary comprehension? If you are new to Python or looking to improve your skills, dictionary comprehension might be a good place to start. A dictionary is a collection of key-value pairs, where each key is a string, and each value is a string, list, or other types of object. You can create and use dictionaries in a variety of ways. The main benefit of dictionary comprehension is that it allows us to write concise and easy-to-understand code. It also allows us to avoid the use of map and filter functions.
In this article, We will discuss in detail what is Python dictionary comprehension, what are the uses and disadvantages, and also provide some examples to help you understand the concepts better. So, if you want to learn more about Python dictionary comprehension, read on.
Learn about How to sort a dictionary value in Python?
Table of Contents
What is Python Dictionary Comprehension?
Dictionary comprehension is a Python feature that allows you to build elegant, concise code by retrieving values from dictionaries. Python dictionary can be used to easily access the keys and values of a dictionary through a specific key without having the actual index.
Why to Use?
This can be useful when you need to get information from several variables at once without having to write multiple lines of code.
You want to filter the items in a list based on specific criteria. For this, you could create an instance of the Dictionary class, specify your filters, and then use the keys() function to retrieve only those items that match your criteria.
Another common scenario involves extracting specific data elements from nested dictionaries. In this case, you would initialize each key with its corresponding value before using the find() function to return exactly what you were looking for.
Example
Following code shows how we can create the dictionary comprehension in python.
square_dict = dict()
# square_dict is dictionary
for n in range(1, 5):
square_dict[n] = n*n
print(square_dict)
The below code shows how we can rewrite the above code example according to the concept of dictionary comprehension, i.e., multiple line code in a single line code.
# dictionary comprehension example
square_dict = {n: n*n for n in range(1, 5)}
print(square_dict) Output
Python Dictionary Comprehension: Conditional Statements
A conditional statement indicates whether action should or should not be taken depending on certain conditions. For example, it refers to the boolean expression determining which code will be executed. If the expression evaluates to True, then code inside the “if” block will run; otherwise, it will not execute. This means that conditionals allow you to test the truth of various statements and decide what actions to take.
1. If Condition
In dictionary comprehension, an “if condition” determines whether a given block of code will be executed. This can be useful for controlling the flow of execution within a program, or it could be used to test data before it is actually used.
The given example will show you how to use if conditional dictionary comprehension in Python.
dict1 = {'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5}
# Check for items greater than 2
dict1_cond = {k:v for (k,v) in dict1.items() if v>3}
print(dict1_cond)
Output
2. Multiple If Condition
Multiple if condition is a Boolean expression that allows multiple conditions to be tested simultaneously. It can be used in conjunction with the else statement to create more flexible and readable code.
Here is the following example that shows you how to code Multiple If condition in dictionary comprehension.
dict = {'Monday': 1, 'tuesday': 2, 'wednesday': 3, 'thursday': 4}
new_dict = {k: v for (k, v) in dict.items() if v % 2 != 0 if v < 4}
print(new_dict)
Output
3. If-Else Condition
An if-else statement is a type of conditional loop that allows you to make choices based on a set of conditions. It works by evaluating one block of code before executing the else clause, and then repeating the process until all blocks have been executed.
Here is the code snippet , that will help you understand better.
dict = {'a': 1, 'b': 2, 'c': 3, 'd': 4, 'e': 5, 'f':6}
# Identify odd and even numbers
dict_if_elseCond = {k:('even' if v%2==0 else 'odd') for (k,v) in dict.items()}
print(dict_if_elseCond)
Output
4. Nested Dictionary
A nested for loop is a programming construct that allows you to iterate over items in an array or dictionary. This can be useful when you want to perform multiple operations on the same set of data.
Below code snippet will guide you how to work with nested dictionary comprehension in Python.
# multiplication of tables in nested dictionary
dict= {
k1: {k2: k1 * k2 for k2 in range(1, 6)} for k1 in range(2, 5)
}
print(dict)
Output
Python Dictionary Comprehension Disadavantages
Dictionary comprehension can be a handy tool in Python, but some disadvantages exist. One of the main drawbacks is that it can be slow and verbose. Additionally, dictionary comprehensions can also be error-prone because they rely on raw string concatenation instead of standard syntactic sugar like parentheses or parenthesis.
FAQs
Is dictionary comprehension faster than For loop ?
When compared to a list comprehension, a dictionary comprehension has less of a performance advantage for realistic problem sizes, and it can and does beat for loops, particularly when targeting a global name.
What is the primary use of the Python dictionary?
Unlike other data types, which only hold a single value as an element, dictionary in Python is an unordered collection of data values used to store data values like a map.
How many types of comprehension are there in Python?
There are 4 types of comprehensions in Python lists, dictionaries, sets, and generators. They’re usually very attractive, brief, and may even enhance the readability of our code most of the time.
Conclusion
As we have seen, the dictionary comprehension feature is flexible as it is a collection of unordered key-value pairs, and it helps you write code concisely that will be understood better. There are four types of comprehension in python. In this article, you have learned about Dictionary Comprehension in detail with example code. I hope this article will be beneficial to your learning. Thanks for reading.
