Python Lists Tutorial

In Python, lists are versatile and widely used to store multiple items in a single variable. As one of the four built-in collection data types, along with Tuple, Set, and Dictionary, lists play a central role in Python programming. Each collection type has unique characteristics and usage scenarios.

Creating a List

Lists in Python are defined using square brackets:

mylist = ["apple", "banana", "cherry"]

You can also define a list like this:

thislist = ["apple", "banana", "cherry"]
print(thislist)

Key Characteristics of Lists

1. Ordered

Lists maintain the order of items as they are inserted. This defined order remains consistent unless explicitly modified using certain methods.

2. Changeable

Python lists are mutable. You can add, remove, or update elements after creation.

3. Allow Duplicates

Since list elements are indexed, they can contain duplicate values:

thislist = ["apple", "banana", "cherry", "apple", "cherry"]
print(thislist)

Determining List Length

Use the len() function to determine how many items a list contains:

thislist = ["apple", "banana", "cherry"]
print(len(thislist))

Data Types in Lists

Python lists can hold elements of various data types, including strings, integers, booleans, or even a combination:

list1 = ["apple", "banana", "cherry"]
list2 = [1, 5, 7, 9, 3]
list3 = [True, False, False]
list4 = ["abc", 34, True, 40, "male"]

Understanding the List Data Type

From Python’s perspective, a list is defined as an object of type 'list':

mylist = ["apple", "banana", "cherry"]
print(type(mylist))

Using the list() Constructor

You can also create a list using the list() constructor:

thislist = list(("apple", "banana", "cherry"))  # Note the double parentheses
print(thislist)

Python Collections Overview

Python supports four primary collection types:

• List: Ordered, changeable, allows duplicates.
• Tuple: Ordered, unchangeable, allows duplicates.
• Set: Unordered, unchangeable (but allows adding/removal), no duplicates.
• Dictionary: Ordered (since Python 3.7), changeable, no duplicates.

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