Exploring Python Dictionary Comprehension Techniques
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Chapter 1: Introduction to Dictionary Comprehension
Dictionary comprehension, similar to list comprehension, enables the creation of dictionaries in a single line of code, promoting brevity and clarity. Let’s explore some practical applications of dictionary comprehension.
Section 1.1: Basic Syntax of Dictionary Comprehension
The fundamental structure for creating a dictionary comprehension is as follows:
{key: 'value' for (key, value) in iterable}
For instance, if we want to generate a dictionary that contains the squares of the first five integers, we can implement it like this:
Dict = {x: x**2 for x in [1, 2, 3, 4, 5]}
print(Dict)
Output:
{1: 1, 2: 4, 3: 9, 4: 16, 5: 25}
Section 1.2: Converting Two Lists into a Dictionary
We can also convert two separate lists into a dictionary by utilizing one list for keys and another for values:
books = ['learning python', 'think python', 'Fluent Python']
authors = ['Mark Lutz', 'Allen B. Downey', 'Luciano Ramalho']
myDict = {k: v for (k, v) in zip(books, authors)}
print(myDict)
Output:
{'learning python': 'Mark Lutz', 'think python': 'Allen B. Downey', 'Fluent Python': 'Luciano Ramalho'}
Subsection 1.2.1: Merging Two Dictionaries
Combining entries from two dictionaries into a single dictionary can be achieved as follows:
books1 = {"learning python": "Mark Lutz", "think python": "Allen B. Downey"}
books2 = {"Fluent Python": "Luciano Ramalho"}
books = {k: v for d in (books1, books2) for k, v in d.items()}
print(books)
Output:
{'learning python': 'Mark Lutz', 'think python': 'Allen B. Downey', 'Fluent Python': 'Luciano Ramalho'}
Section 1.3: Creating Nested Dictionaries
We can also construct a nested dictionary using comprehension:
dictionary = {
k1: {k2: k1 * 4 * k2 for k2 in range(1, 6)} for k1 in range(2, 5)
}
print(dictionary)
Here, we first multiply 2 by 4 and then by each number from 1 to 5, and repeat this for 3 and 4.
Output:
{2: {1: 8, 2: 16, 3: 24, 4: 32, 5: 40}, 3: {1: 12, 2: 24, 3: 36, 4: 48, 5: 60}, 4: {1: 16, 2: 32, 3: 48, 4: 64, 5: 80}}
Chapter 2: Conditional Logic in Dictionary Comprehension
Using conditional logic within dictionary comprehension allows for more tailored data structures.
Video: Python dictionary comprehension - A quick guide on conditional logic in dictionary comprehension.
For example, to filter and print only even numbers, we can apply a conditional:
old = {1: "odd", 2: "even", 3: "odd", 4: "even"}
new = {k: v for (k, v) in old.items() if k % 2 == 0}
print(new)
Output:
{2: 'even', 4: 'even'}
Section 2.1: Implementing If-Else Conditions
We can also utilize if-else statements to classify data within a dictionary:
blood_pressure = {"A": 115, "B": 160, "C": 125}
new_dict_1 = {k: ('normal' if v <= 120 else 'high' if 120 <= v <= 129 else 'elevated') for (k, v) in blood_pressure.items()}
print(new_dict_1)
Output:
{'A': 'normal', 'B': 'high', 'C': 'elevated'}
This example demonstrates how we can categorize blood pressure readings based on specified thresholds.
Video: Python Dictionary Comprehensions - An overview of advanced usage and best practices.
For further exploration of Python dictionary comprehension, consider checking out additional resources and tutorials.