Day 22/100: Useful List Methods in Python (append, pop, sort, and more)

Welcome to Day 22 of the 100 Days of Python series!
Yesterday, you learned how to create and manipulate lists. Today, we’ll go deeper into the most commonly used list methods that make lists a truly powerful tool in Python.

If you want to write cleaner, more Pythonic code, mastering these methods is essential. Let’s go! 🐍

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📦 What You’ll Learn

• Key list methods: append(), insert(), remove(), pop(), sort(), and more
• Real-world examples for each
• When to use which method
• Best practices and common mistakes

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🔧 1. append() – Add Item to End of List

fruits = ["apple", "banana"]
fruits.append("cherry")
print(fruits)  # ['apple', 'banana', 'cherry']

✅ Use when you want to add something to the end of a list.

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📍 2. insert(index, item) – Add at Specific Position

fruits.insert(1, "orange")
print(fruits)  # ['apple', 'orange', 'banana', 'cherry']

✅ Use when position matters (e.g., inserting a task at the top of a to-do list).

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❌ 3. remove(item) – Remove by Value

fruits.remove("banana")
print(fruits)  # ['apple', 'orange', 'cherry']

⚠️ Raises an error if the item is not in the list.

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🧹 4. pop(index) – Remove by Index (and Get the Item)

last_item = fruits.pop()  # Removes last item
print(last_item)          # 'cherry'

second_item = fruits.pop(1)  # Removes index 1
print(second_item)           # 'orange'

✅ Useful when you want to both remove and retrieve an item.

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🔁 5. clear() – Remove All Items

fruits.clear()
print(fruits)  # []

✅ Great for resetting a list in-place.

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🔄 6. sort() – Sort List In-Place (Ascending)

numbers = [5, 2, 9, 1]
numbers.sort()
print(numbers)  # [1, 2, 5, 9]

⚠️ Modifies the original list!

For descending order:

numbers.sort(reverse=True)

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🧪 7. sorted() – Return a New Sorted List

nums = [4, 1, 7]
new_nums = sorted(nums)
print(new_nums)  # [1, 4, 7]
print(nums)      # [4, 1, 7]

✅ Use when you want to keep the original list unchanged.

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🔁 8. reverse() – Reverse the List In-Place

nums = [1, 2, 3]
nums.reverse()
print(nums)  # [3, 2, 1]

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📊 9. count(item) – Count Occurrences

names = ["Alice", "Bob", "Alice"]
print(names.count("Alice"))  # 2

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🔍 10. index(item) – Get Index of First Occurrence

names = ["Alice", "Bob", "Alice"]
print(names.index("Bob"))  # 1

⚠️ Raises ValueError if the item is not found.

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➕ 11. extend() – Merge Two Lists

a = [1, 2]
b = [3, 4]
a.extend(b)
print(a)  # [1, 2, 3, 4]

✅ Use instead of + if you want to add in-place.

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💡 Summary Table

Method	Purpose	Modifies Original?
append()	Add to end	✅ Yes
insert()	Add at position	✅ Yes
remove()	Remove by value	✅ Yes
pop()	Remove by index + return	✅ Yes
clear()	Empty the list	✅ Yes
sort()	Sort list in-place	✅ Yes
sorted()	Return sorted copy	❌ No
reverse()	Reverse in-place	✅ Yes
count()	Count value	❌ No
index()	Return index of value	❌ No
extend()	Add another list’s items	✅ Yes

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🧠 Recap

Today you learned:

• How to use Python’s most common list methods
• When to use append() vs extend(), sort() vs sorted()
• Best practices for modifying and accessing list elements

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