🔤 How to Sort a List in Python – Master sort() and sorted() | TechTown.in
Sorting a list is a fundamental task in Python, whether you’re arranging names alphabetically, scores in descending order, or filtering product prices. Python gives you powerful tools to sort lists easily — both in-place and by returning a new sorted copy.
In this tutorial, we’ll explore how to sort Python lists using sort(), sorted(), custom key functions, and how to sort in reverse order.
🔹 1. Use sort() to Sort a List (In-Place)
The simplest way to sort a list is by using the sort() method. It modifies the original list.
Example:
fruits = ["banana", "apple", "cherry"]
fruits.sort()
print(fruits) # ['apple', 'banana', 'cherry']
✅ The list is now sorted in ascending (alphabetical) order.
🔄 2. Sort in Reverse Order
You can sort the list in descending order using reverse=True.
numbers = [100, 50, 25, 75]
numbers.sort(reverse=True)
print(numbers) # [100, 75, 50, 25]
📦 3. Use sorted() to Keep Original List Untouched
Unlike sort(), the sorted() function returns a new list, keeping the original unchanged.
names = ["John", "Alice", "Bob"]
sorted_names = sorted(names)
print(sorted_names) # ['Alice', 'Bob', 'John']
print(names) # ['John', 'Alice', 'Bob']
✅ Great when you want to keep the original list intact.
🧠 4. Sort with Custom Key Functions
Use the key= parameter to define custom sorting logic.
Sort by Length:
words = ["banana", "kiwi", "apple"]
words.sort(key=len)
print(words) # ['kiwi', 'apple', 'banana']
Sort by Last Letter:
words.sort(key=lambda x: x[-1])
print(words)
🔢 5. Sort a List of Numbers
Python sorts integers and floats just like strings:
scores = [70, 90, 50, 100]
scores.sort()
print(scores) # [50, 70, 90, 100]
🚫 Mixed Data Types Can’t Be Sorted
You can’t sort a list with incompatible types:
items = ["apple", 10, True]
items.sort() # ❌ TypeError
✅ Keep list items uniform in type for sorting.
🧪 Real-World Example – Sorting a Dictionary by Value
Sort list of tuples or dictionary items:
products = [("pen", 10), ("notebook", 50), ("eraser", 5)]
products.sort(key=lambda x: x[1])
print(products) # [('eraser', 5), ('pen', 10), ('notebook', 50)]
🧠 Summary – Sorting in Python
| Method | Description | Changes Original? |
|---|---|---|
list.sort() | Sorts the list in-place | ✅ Yes |
list.sort(reverse=True) | Sort in descending order | ✅ Yes |
sorted(list) | Returns a new sorted list | ❌ No |
key=func | Sort using custom logic | Optional |
🏁 Final Thoughts
Sorting is a critical skill in Python, used in everything from reports to leaderboards. With just a few lines of code, you can organize your data your way using sort() or sorted() — and even apply your own logic with custom key functions.
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