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Learn Python: Sets

rishiabee profile image Rishi ・2 min read

A set is another type of collection like list and tuple.

So what are sets?

  • Sets are unordered – Items stored in a set aren’t kept in any particular order.
  • Set items are unique – Duplicate items are not allowed.
  • Sets are unindexed – You cannot access set items by referring to an index.
  • Sets are changeable (mutable) – They can be changed in place, can grow and shrink on demand.

The values of a set are defined within curly braces { }.
A quick reminder:

  • For list, we use square brackets [ ].
  • For tuple, we use brackets ( ).
fruits = {'apple','orange'}
print(fruits);

Sets don't maintain order. Every time we execute the code, the order of the values in the set changes.

Do note, in the example below we are adding pineapple multi times, but when we print the set, we only see pineapple once. This is because set does not allow duplicate.

fruits = {'apple','orange'}
fruits.add('pineapple');
fruits.add('pineapple');
fruits.add('pineapple');
print(fruits);



Benefits of sets

The key benefit of sets is that they make comparing values between two sets easier.

Set Operations

Sets are commonly used for computing mathematical operations such as intersection, union, difference, and symmetric difference.

Difference

basket_1 = {"Strawberry", "Cherry", "Apple", "Grapes"}
basket_2 = {"Pear", "Avocado", "Lime", "Apple", "Grapes"}

# Difference  
basket_1_difference = basket_1.difference(basket_2);
basket_2_difference = basket_2.difference(basket_1);

print(basket_1_difference);
print(basket_2_difference);

Symmetric Difference

basket_1 = {"Strawberry", "Cherry", "Apple", "Grapes"}
basket_2 = {"Pear", "Avocado", "Lime", "Apple", "Grapes"}

# Symmetric Difference 
basket_1_symmetric_difference = basket_1.symmetric_difference(basket_2);
basket_2_symmetric_difference = basket_2.symmetric_difference(basket_1);
print(basket_1_symmetric_difference);
print(basket_2_symmetric_difference);

Intersection

basket_1 = {"Strawberry", "Cherry", "Apple", "Grapes"}
basket_2 = {"Pear", "Avocado", "Lime", "Apple", "Grapes"}

# Intersection
basket_1_intersection = basket_1.intersection(basket_2);
print(basket_1_intersection);

Union

basket_1 = {"Strawberry", "Cherry", "Apple", "Grapes"}
basket_2 = {"Pear", "Avocado", "Lime", "Apple", "Grapes"}

# Union
basket_1_union = basket_1.union(basket_2);
print(basket_1_union);



Discussion (6)

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waylonwalker profile image
Waylon Walker

Sets are one of my favorite container types. You can do really powerful operations with very little effort, and they are wicked fast at it.

The one thing that I see your missing is the set operators like + * - | ^

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rishiabee profile image
Rishi Author

Waylon, Thanks!
Will definitely include that in another article about advance features of sets.

Much appreciated. Thanks.

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waylonwalker profile image
Waylon Walker

As much as I like the tersness of the operators, and being able to quickly compare datasets ad-hoc, using the method names can be much more readable and less confusing. Good call to use those. I guess its worth a mention because you will run into them into the wild.

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ben profile image
Ben Halpern

Love the use of replit here

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rishiabee profile image
Rishi Author

Javier,
Thank for your input, much appreciated.
I'm taking note, I'll definitely add that when I review it.

Again, thanks!