How do I declare an array in Python?

python

list-comprehensions

data-structures

performance-optimization

byAlex Kataev·Nov 23, 2024

In Python, you can use lists to create arrays:

# How many programmers does it take to change a light bulb? None, that's a hardware issue.
my_list = [1, 2, 3]

For 2D arrays or matrices:

# I would tell you a joke about UDP...but you might not get it ;)
my_matrix = [[1, 2], [3, 4]]

If performance and single-type data is a concern, consider array.array:

from array import array
# Knock, knock. Who’s there? very long pause…. Java.
my_array = array('i', [1, 2, 3])

Choose numpy for scientific computing or multidimensional arrays:

import numpy as np
# If I had a cent for every time I forgot an item on my shopping list, I'd get a dollar by now!
my_np_array = np.array([1, 2, 3])

Differences between arrays and lists

Though they appear similar, arrays and lists have distinct features:

Python lists: Dynamic in size, includes various types, and supports negative indexing
array.array: Requires homogeneous data for efficient storage and performance; consult the array module documentation

Your choice depends upon the task:

Tips for seasoned Python users:

Initialize lists using list comprehensions:

# Zero heroes
zeroes = [0 for _ in range(10)]

Pre-allocate storage space for heavy data to increase efficiency.
Though Python is dynamically typed, enforce type discipline when needed every once in a while. Remember, consistency is a virtue!

Python offers several other handy structures:

Consider the Python proficiency of the reader:

For beginners: Simple examples and explanations should suffice.
For the experienced ones: Time to dive deep into intricacies and performance-related aspects.

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