More on Lists

Let’s dive deeper into lists in Python! 📝🐍

What is a List? 📋

A list is an ordered, mutable collection of items. Lists can hold items of any type (numbers, strings, even other lists) and can be changed after creation (add, remove, or modify elements)¹.

• Ordered: Items keep their position.
• Mutable: You can change the content.
• Heterogeneous: Can contain different data types.

Creating a List 🛠️

my_list = [1, "apple", 3.14, True]

Accessing List Elements 🔍

• Indexing (starts at 0):

print(my_list[^1])  # Output: apple

• Negative Indexing (from the end):

print(my_list[-1])  # Output: True

• Slicing:

print(my_list[1:3])  # Output: ['apple', 3.14]

Modifying Lists ✏️

• Change an element:

my_list[^0] = 100
print(my_list)  # Output: [100, 'apple', 3.14, True]

• Add elements:
  • append() – Adds to the end
  • insert() – Adds at a specific position
  • extend() – Adds all elements from another list

my_list.append("banana")
my_list.insert(1, "orange")
my_list.extend([7, 8])

• Remove elements:
  • remove() – Removes by value
  • pop() – Removes by index (default: last)
  • del – Deletes by index or slice

my_list.remove("apple")
my_list.pop(2)
del my_list[^0]

Common List Methods 🧰

List Operations ⚡

• Concatenation: a + b
• Repetition: a * 3
• Membership: x in a
• Length: len(a)
• Iteration: for item in a:

List Comprehensions 🏗️

A compact way to create lists:

squares = [x*x for x in range(5)]
print(squares)  # Output: [0, 1, 4, 9, 16]

Practice Questions & Solutions 📝

1️⃣ Create a list of numbers from 1 to 5. Print the third element.

numbers = [1, 2, 3, 4, 5]
print(numbers[^2])  # Output: 3

2️⃣ Add “grape” to the end of this list: fruits = ["apple", "banana"]

fruits = ["apple", "banana"]
fruits.append("grape")
print(fruits)  # Output: ['apple', 'banana', 'grape']

3️⃣ Remove the first element from the list: data =

data = [10, 20, 30, 40]
del data[^0]
print(data)  # Output: [20, 30, 40]

4️⃣ Sort the list nums = [^3][^2][^4][^1] in ascending order.

nums = [3, 1, 4, 2]
nums.sort()
print(nums)  # Output: [1, 2, 3, 4]

5️⃣ Use a list comprehension to create a list of even numbers from 0 to 10.

evens = [x for x in range(11) if x % 2 == 0]
print(evens)  # Output: [0, 2, 4, 6, 8, 10]

Key Points with Emojis 🎯

• Lists are mutable and ordered 📚
• Use [] to create, and methods like append(), remove(), sort()
• Can contain any type of data, even other lists 🥗
• Indexing starts at 0
• List comprehensions make building lists easy! 🏗️

If you want to know more or try advanced list tricks, just ask! 😊

References: Lists are mutable, ordered, and can hold any type of object. They support indexing, slicing, concatenation, repetition, and many built-in methods for modification and querying²¹.