Python List Comprehensions Reference
List comprehensions provide a concise way to create lists in Python. Here are some practical examples:
1. Basic List Comprehension
# Create a list of squares
squares = [x**2 for x in range(10)]
print(squares) # [0, 1, 4, 9, 16, 25, 36, 49, 64, 81]
# Convert temperatures (Celsius to Fahrenheit)
celsius = [0, 10, 20, 30, 40]
fahrenheit = [(temp * 9/5) + 32 for temp in celsius]
print(fahrenheit) # [32.0, 50.0, 68.0, 86.0, 104.0]
2. Filtering with Comprehensions
# Get even numbers from a list
numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
even_numbers = [x for x in numbers if x % 2 == 0]
print(even_numbers) # [2, 4, 6, 8, 10]
3. Nested List Comprehension
# Create a matrix
matrix = [[j for j in range(3)] for i in range(3)]
print(matrix) # [[0, 1, 2], [0, 1, 2], [0, 1, 2]]
4. String Manipulation
# Convert words to uppercase
words = ['hello', 'world', 'python']
uppercase_words = [word.upper() for word in words]
print(uppercase_words) # ['HELLO', 'WORLD', 'PYTHON']
Key Takeaways
- List comprehensions offer a compact syntax for list creation
- They can include filtering conditions
- They can transform elements during creation
- They can be nested for more complex operations