Video link: https://youtu.be/-vfzvT0Fh0A
In this video, we learned about a compound data type in Python called set.
Programs in the Video
- Creating Sets
- Add Items to a Set
- Remove Items from a Set
- Check if an item is in a Set
- Iterating Through a Set
- Python Set Operations
- Task: Guess the Output
Similar to a set in mathematics, a Python set is a collection of non-duplicate and immutable items in no particular order.
To create a set, we put items separated by a colon , inside the curly braces {}.
animals = {"dog", "cat", "tiger", "elephant"}
print(animals)Output
{'cat', 'dog', 'tiger', 'elephant'}
If we add duplicate items,
animals = {"dog", "cat", "tiger", "elephant", "dog"}
print(animals)Output
{'cat', 'dog', 'tiger', 'elephant'}
We can see that there is only one dog as sets don't have duplicate items.
Notes:
- The order of items is different from how we defined them because sets are unordered.
- We can create an empty set using
set(). We cannot use{}because it creates an empty dictionary.
Sets in Python are mutable. We can add and remove items from them.
To add a single item to a set, we use the add() method.
animals = {"dog", "cat", "tiger", "elephant", "dog"}
animals.add("monkey")
print(animals)Output
{'tiger', 'monkey', 'cat', 'dog', 'elephant'}
We can also add all the items of iterables like lists, tuples, and other sets to a set. For that, we use the update() method.
animals = {"dog", "tiger", "elephant"}
wild_animals = ["tiger", "leopard", "elephant"]
animals.update(wild_animals)
print(animals)Output
{'tiger', 'dog', 'cat', 'elephant', 'leopard'}
We can also pass multiple iterables to the update() method:
animals = {"dog", "tiger", "elephant"}
wild_animals = ["tiger", "leopard", "elephant"]
animals.update(wild_animals, {"dolphin"})
print(animals)Output
{'dog', 'dolphin', 'leopard', 'elephant', 'tiger'}
To remove an item in a set, we can either use the discard() method or the remove() method.
However, there is an important difference between them. If the item we are trying to remove is not in the set, discard() returns None, whereas, the remove() method throws an error.
animals = {"tiger", "cat", "elephant", "dog"}
animals.remove("ferret")
print(animals)Output
Traceback (most recent call last):
File "<string>", line 2, in <module>
KeyError: 'ferret'
Meanwhile,
animals = {"tiger", "cat", "elephant", "dog"}
animals.discard("ferret")
print(animals)Output
{'tiger', 'elephant', 'cat', 'dog'}
We can also remove all items in a set at once by using the clear() method.
animals = {"tiger", "cat", "elephant", "dog"}
animals.clear()
print(animals)Output
set()
Similar to other compound data types, we can check if an item is in a set or not by using the in keyword.
For example,
animals = {"tiger", "cat", "elephant", "dog"}
print("tiger" in animals)
print("ferret" in animals)Output
True
False
Similar to other sequences, we can easily iterate through items of a set by using a for loop.
animals = {"tiger", "cat", "elephant", "dog"}
for animal in animals:
print(animal)Output
elephant
dog
tiger
cat
The items of the set are printed one by one. However, the order in which these items are printed is random
Python sets have same properties to that of sets in mathematics. Let's look at some set operations.
The union of two sets is a set of all items in both the sets.
To find the union of sets, we can either use the union() method or the pipe symbol |.
domestic_animals = {"dog", "cat", "elephant"}
wild_animals = {"lion", "tiger", "elephant"}
animals = domestic_animals.union(wild_animals)
animals1 = animals = domestic_animals | wild_animals
print(animals)
print(animals1)Output
{'tiger', 'elephant', 'dog', 'cat', 'lion'}
{'tiger', 'elephant', 'dog', 'cat', 'lion'}
The intersection of two sets is a set of items that are common in both sets.
To find the union of sets, we can either use the intersection() method or the ampersand symbol &.
domestic_animals = {"dog", "cat", "elephant"}
wild_animals = {"lion", "tiger", "elephant"}
common_animals = domestic_animals.intersection(wild_animals)
common_animals1 = domestic_animals & wild_animals
print(common_animals)
print(common_animals1)Output
{'elephant'}
{'elephant'}
Can you guess the output of this program?
animals = {"dog", "cat", "tiger", "elephant", "dog"}
print("1.", animals)
animals.remove("cat")
animals.remove("dog")
print("2.", animals)
animals.add("snake")
print("3.", animals)
result = {1, 5, 10} & {100, 10, 3, 5}
print("4.", result)Output
1. {'dog', 'cat', 'tiger', 'elephant'}
2. {'tiger', 'elephant'}
3. {'elephant', 'snake', 'tiger'}
4. {10, 5}