PYTHON
Concise Dictionary Creation and Transformation with Comprehensions
Learn to build and transform dictionaries efficiently using dictionary comprehensions in Python. Ideal for quick data restructuring, filtering, and mapping key-value pairs.
students_scores = {'Alice': 88, 'Bob': 92, 'Charlie': 75, 'David': 95}
# 1. Create a new dictionary from an existing one, filtering and transforming values
# Get students who scored 90+ and assign 'A' grade
high_achievers = {
name: 'A' for name, score in students_scores.items() if score >= 90
}
print(f"High achievers (A grade): {high_achievers}")
# 2. Swap keys and values (if values are unique)
score_to_student = {
score: name for name, score in students_scores.items()
}
print(f"Scores mapped to students: {score_to_student}")
# 3. Create a dictionary from two lists (keys and values)
keys = ['apple', 'banana', 'cherry']
values = [1.2, 0.8, 2.5]
fruit_prices = {
key: value for key, value in zip(keys, values)
}
print(f"Fruit prices: {fruit_prices}")
# 4. Conditional key-value transformation
status_by_score = {
name: 'Excellent' if score >= 90 else 'Good' for name, score in students_scores.items()
}
print(f"Student status by score: {status_by_score}")
How it works: Dictionary comprehensions provide a powerful and expressive syntax for creating new dictionaries. This snippet illustrates how to efficiently filter key-value pairs, transform values, swap keys and values, and construct dictionaries from iterables like lists. They are a concise and Pythonic alternative to traditional loops, enhancing both code clarity and performance when generating or manipulating dictionary data.