List Methods

📋 List Methods in Python 🐍

🔹 What Are List Methods? 🤔

List methods are built-in functions that allow you to perform operations on lists. They help you add, remove, sort, and modify items in your lists without needing to write complex code.

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1️⃣ Adding Items to a List ➕

a. append(item)

• Description: Adds an item to the end of the list.
• Example:

fruits = ["apple", "banana", "cherry"]
fruits.append("orange")  # Adds 'orange' to the end
print(fruits)  # Output: ['apple', 'banana', 'cherry', 'orange']

b. insert(index, item)

• Description: Inserts an item at the specified index in the list.
• Example:

fruits = ["apple", "banana", "cherry"]
fruits.insert(1, "kiwi")  # Inserts 'kiwi' at index 1
print(fruits)  # Output: ['apple', 'kiwi', 'banana', 'cherry']

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2️⃣ Removing Items from a List ❌

a. remove(item)

• Description: Removes the first occurrence of the specified item from the list.
• Example:

fruits = ["apple", "banana", "cherry"]
fruits.remove("banana")  # Removes 'banana'
print(fruits)  # Output: ['apple', 'cherry']

b. pop(index)

• Description: Removes and returns the item at the specified index. If no index is specified, it removes the last item.
• Example:

fruits = ["apple", "banana", "cherry"]
last_fruit = fruits.pop()  # Removes the last item
print(last_fruit)  # Output: cherry
print(fruits)  # Output: ['apple', 'banana']

removed_fruit = fruits.pop(0)  # Removes the item at index 0
print(removed_fruit)  # Output: apple
print(fruits)  # Output: ['banana']

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3️⃣ Modifying Items in a List ✏️

a. extend(iterable)

• Description: Adds all elements from an iterable (like a list or tuple) to the end of the list.
• Example:

fruits = ["apple", "banana"]
fruits.extend(["cherry", "orange"])  # Adds items from the list
print(fruits)  # Output: ['apple', 'banana', 'cherry', 'orange']

b. sort()

• Description: Sorts the items in the list in ascending order.
• Example:

fruits = ["banana", "apple", "cherry"]
fruits.sort()  # Sorts the list
print(fruits)  # Output: ['apple', 'banana', 'cherry']

c. reverse()

• Description: Reverses the order of the items in the list.
• Example:

fruits = ["apple", "banana", "cherry"]
fruits.reverse()  # Reverses the list
print(fruits)  # Output: ['cherry', 'banana', 'apple']

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4️⃣ Finding List Information 🔍

a. index(item)

• Description: Returns the index of the first occurrence of the specified item.
• Example:

fruits = ["apple", "banana", "cherry"]
index_of_banana = fruits.index("banana")
print(index_of_banana)  # Output: 1

b. count(item)

• Description: Returns the number of times the specified item appears in the list.
• Example:

fruits = ["apple", "banana", "cherry", "banana"]
count_of_banana = fruits.count("banana")
print(count_of_banana)  # Output: 2

c. clear()

• Description: Removes all items from the list.
• Example:

fruits = ["apple", "banana", "cherry"]
fruits.clear()  # Clears the list
print(fruits)  # Output: []

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5️⃣ List Comprehension 🔄

While not a method, list comprehension is a powerful feature in Python that allows you to create new lists by applying an expression to each item in an existing list.

Example:

numbers = [1, 2, 3, 4]
squared_numbers = [x**2 for x in numbers]  # Squaring each number
print(squared_numbers)  # Output: [1, 4, 9, 16]

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✅ Summary

• List methods help you manage and manipulate lists efficiently.
• You can add items using append() and insert(), remove items using remove() and pop(), and modify the list with extend(), sort(), and reverse().
• You can find the index of an item with index(), count occurrences with count(), and clear the entire list with clear().

numbers = [1, 2, 3, 7, 5, 20]
numbers.append(30) # 30 will added to the end of the list
numbers.insert(0, 30) # 30 will be added in the beginner of the list, the first parameter is the index
numbers.insert(1, 30) # 30 will be added in the index 1 of the list
numbers.remove(5) # item with the value 5 will be removed from the list
numbers.clear() # will remove all the item in the list
numbers.pop() # this will remove the last item  in the list
numbers.index(3) # check the index of the value - output 2
numbers.count(5) # this will check the number of value in the list -> 1
numbers.sort() # this will sort the value in the List 
numbers.reverse() # will reverse your sort list value
numbers2 = numbers.copy() #  copy the list to another list

• we also can check the existing of the value in the list by using in

numbers = [1,2,3,4,5,67,8]
print(50 in numbers) # output -> False

-Example

numbers = [2, 2, 4, 6, 3, 4, 6, 1]
uniques = []
for number in numbers:
    if number not in uniques:
       uniques.append(number)
print(uniques) # output -> 2,4,6,3,1