When working with sets in Python, the real magic happens when you start comparing them. Just like overlapping guest lists, playlists, or even shopping baskets, you’ll often want to know what’s shared, what’s unique, or what happens when you combine them. Python makes this easy with four handy operations: union, intersection, difference, and symmetric difference. Each one gives you a different way to compare sets, and together they unlock loads of practical problem-solving power.
Union
The union of two sets combines everything from both, removing duplicates automatically. It’s like merging two guest lists into one.
Example:
a = {1, 2, 3}
b = {3, 4, 5}
print(a.union(b)) # {1, 2, 3, 4, 5}
Try it yourself:
- Make two sets of fruits.
- Union them together.
- See how duplicates are handled.
Intersection
The intersection finds only the items both sets share. Think of it as asking, “who’s on both the football and chess team?”
Example:
a = {1, 2, 3}
b = {2, 3, 4}
print(a.intersection(b)) # {2, 3}
Try it yourself:
- Create two sets of colours.
- Find the intersection.
- Change one set and see how results change.
Difference
The difference shows what’s in one set but not the other. It’s like finding who came to one party but skipped the other.
Example:
a = {1, 2, 3, 4}
b = {3, 4}
print(a.difference(b)) # {1, 2}
Try it yourself:
- Create two sets of animals.
- Use
.difference()to see which are only in the first. - Reverse the difference and compare.
Symmetric Difference
The symmetric difference shows what’s unique to each set — everything except the overlap. It’s like finding the non-shared songs in two playlists.
Example:
a = {1, 2, 3}
b = {3, 4, 5}
print(a.symmetric_difference(b)) # {1, 2, 4, 5}
Try it yourself:
- Make two sets of numbers.
- Use
.symmetric_difference(). - Add another common number to both sets and observe the change.
