Python List Data Type

In Python, a List is a mutable sequence data type that allows you to store multiple values in a single variable. Lists are stored in brackets [] and values are separated by commas, allowing you to mix various data types. For example:

my_list = [1, 2, 3, "hello", True, 3.14]

Features of Lists

1. Indexing and Slicing

Each element of a list can be accessed via indexing. Python’s indexing starts at 0, and negative indexes can be used to access elements from the end.

numbers = [10, 20, 30, 40, 50]
print(numbers[0])   # 10
print(numbers[-1])  # 50 (last element)

Slicing to retrieve a portion of the list is also possible.

print(numbers[1:4])  # [20, 30, 40]
print(numbers[:3])     # [10, 20, 30]
print(numbers[2:])     # [30, 40, 50]

2. List Operations

Lists can be combined with the + operator and repeated with the * operator.

list1 = [1, 2, 3]
list2 = [4, 5, 6]
combined = list1 + list2  # [1, 2, 3, 4, 5, 6]
repeated = list1 * 2      # [1, 2, 3, 1, 2, 3]

3. Mutability of Lists

Lists are mutable data types, allowing you to add, modify, and delete elements. This mutability makes lists very useful for manipulating data easily.

my_list = [1, 2, 3]
my_list[1] = 20          # [1, 20, 3]
my_list.append(4)        # [1, 20, 3, 4]
my_list.insert(1, 15)    # [1, 15, 20, 3, 4]
my_list.remove(3)        # [1, 15, 20, 4]

4. List Methods

There are various built-in methods for lists that are useful for manipulating them. Here are some common list methods:

list.append(x): Add an element to the end of the list
list.insert(i, x): Insert an element at a specific position
list.remove(x): Remove the first occurrence of a specific element from the list
list.pop(i): Remove and return the element at a specific position (i if not provided, removes the last element)
list.index(x): Return the first position of a specific element
list.sort(): Sort the list in ascending order
list.reverse(): Reverse the order of the elements in the list

my_list = [3, 1, 4, 1, 5, 9]
my_list.sort()        # [1, 1, 3, 4, 5, 9]
my_list.reverse()     # [9, 5, 4, 3, 1, 1]
my_list.pop()         # 1, list is now [9, 5, 4, 3, 1]

5. List Comprehension

List Comprehension is a concise way to create lists, allowing you to utilize loops and conditionals to generate a new list.

squares = [x * x for x in range(1, 6)]  # [1, 4, 9, 16, 25]
filtered = [x for x in range(10) if x % 2 == 0]  # [0, 2, 4, 6, 8]

Summary

Lists are a data type that can store multiple values in a single variable, with mutable features.
You can access list elements through indexing and slicing.
Lists support concatenation (+) and repetition (*) operations.
You can add, modify, and delete elements using various list methods.
List comprehension can be used to create lists concisely.

Lists are one of the most commonly used data types in Python, making them very useful for storing and manipulating data. Utilize the various features of lists to write more efficient code!

Python Basic Data Types: List