🔁 Python Sets – Create, Modify, and Use Set Operations
🧲 Introduction – What Is a Set in Python?
A set in Python is an unordered, unindexed collection that stores only unique elements. It’s ideal for deduplication, fast membership tests, and performing set-theory operations like union, intersection, and difference.
Unlike lists or tuples, sets are mutable (can be changed) but do not allow duplicates or maintain order.
🎯 In this guide, you’ll learn:
- How to create, access, and modify Python sets
- Core set operations like union and intersection
- Methods for copying, joining, and updating sets
- Real-world applications with exercises
📌 Topics Covered
| 🧩 Topic | 📘 Description |
|---|---|
| Python Sets: Access / Add / Remove | Creating sets, adding/removing elements, and accessing items |
| Python Loop Sets | Iterating through sets |
| Python Copy / Join Sets | Duplicating and combining sets |
| Python Set Operators | Union, intersection, difference, symmetric difference |
| Python Set Methods | Built-in methods for set manipulation |
| Python Set Exercises | Practice problems to test understanding |
🧰 Creating Sets in Python
fruits = {"apple", "banana", "cherry"}
print(fruits)
✅ Explanation:
- Sets use
{}or theset()constructor. - Duplicates are automatically removed.
🔹 Using set() Constructor
numbers = set([1, 2, 3, 2])
print(numbers) # Output: {1, 2, 3}
✅ Converts any iterable (like list/tuple) into a set.
🔍 Accessing and Looping Through Sets
🔹 Loop through elements:
for fruit in fruits:
print(fruit)
✅ Sets are unordered, so the order may change with every execution.
🧪 Adding and Removing Elements
✅ add() – Add a single item:
fruits.add("orange")
✅ update() – Add multiple items:
fruits.update(["grape", "melon"])
✅ remove() – Remove item, raises error if not found:
fruits.remove("banana")
✅ discard() – Remove item safely:
fruits.discard("kiwi")
🔁 Set Operations – Algebraic Power
✅ Union (| or .union())
a = {1, 2, 3}
b = {3, 4, 5}
print(a | b) # {1, 2, 3, 4, 5}
✅ Intersection (& or .intersection())
print(a & b) # {3}
✅ Difference (- or .difference())
print(a - b) # {1, 2}
✅ Symmetric Difference (^ or .symmetric_difference())
print(a ^ b) # {1, 2, 4, 5}
🔐 Set Methods Summary
| Method | Description |
|---|---|
add() | Add one item |
update() | Add multiple items |
remove() | Remove item (error if not found) |
discard() | Remove item (no error if not found) |
pop() | Remove a random item |
clear() | Empty the set |
union() | Combine two sets |
intersection() | Common elements |
difference() | Elements in one set but not the other |
symmetric_difference() | Elements in either set but not both |
🧠 Best Practices
✅ Use set() to remove duplicates from lists/tuples.
✅ Use discard() instead of remove() to avoid runtime errors.
✅ Leverage set math for clean filtering and comparison.
✅ Convert data from files/inputs to sets for faster lookups.
🧪 Python Set Exercises
🔹 1. Remove Duplicates from a List
nums = [1, 2, 2, 3, 4, 4]
unique = list(set(nums))
print(unique)
🔹 2. Find Common Items Between Two Sets
a = {"a", "b", "c"}
b = {"b", "c", "d"}
print(a & b)
🔹 3. Combine Two Sets and Remove Duplicates
x = {1, 2}
y = {2, 3}
print(x | y)
🔹 4. Filter Items Not in Both Sets
x = {1, 2, 3}
y = {3, 4, 5}
print(x ^ y)
🔹 5. Safely Remove an Element
items = {"pen", "pencil", "eraser"}
items.discard("marker") # no error
print(items)
📌 Summary – Recap & Next Steps
Python sets offer unmatched performance for deduplication, fast lookups, and set-theoretic logic. With support for union, intersection, and difference operations, sets are a powerful tool for solving many programming challenges efficiently.
🔍 Key Takeaways:
- Sets store unique, unordered elements.
- Use
.add(),.update(),.remove(),.discard()to manage items. - Perform set math using operators:
|,&,-,^. - Use sets to filter data and validate membership.
⚙️ Real-World Relevance:
Sets are used in data science, validation checks, permission systems, and duplicate removal in large datasets.
❓ FAQ Section – Python Sets
❓ What is a set in Python?
✅ A set is an unordered collection of unique items. Defined with {} or set().
❓ Can sets contain duplicates?
✅ No. Any repeated values are automatically removed.
❓ What’s the difference between remove() and discard()?
✅ remove() raises an error if the item doesn’t exist; discard() does not.
❓ How to remove duplicates from a list using sets?
✅ Convert it:
list(set([1, 2, 2, 3])) # Output: [1, 2, 3]
❓ Are sets mutable?
✅ Yes. You can add/remove elements. For immutability, use frozenset.
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