< Sets
String Methods >

In Python, a set is a collection of unique items. A set does not allow duplicate values, and it is unordered, meaning the items in a set are not stored in any specific order. Sets are used when you want to store multiple items, but each item should only appear once.

You can create a set in Python using curly braces {} or the set() function.

Creating a Set

Here’s how to create a set:

# Creating a set using curly braces
fruits = {"apple", "banana", "cherry"}
print(fruits)

Output:

{'banana', 'cherry', 'apple'}

Notice that the order of items can be different every time you print a set. This is because sets are unordered.

Adding Items to a Set

To add items to a set, we use the add() method. This method adds a single item to the set.

# Adding an item to the set
fruits.add("orange")
print(fruits)

Output:

{'banana', 'cherry', 'apple', 'orange'}

If you try to add an item that already exists in the set, Python will simply ignore it.

fruits.add("apple")
print(fruits)

Output:

{'banana', 'cherry', 'apple', 'orange'}

Notice that the item “apple” was not added again because sets don’t allow duplicates.

Removing Items from a Set

There are several methods to remove items from a set:

  1. remove(): Removes a specific item. If the item doesn’t exist in the set, it raises an error.
# Removing an item from the set
fruits.remove("banana")
print(fruits)

Output:

{'cherry', 'apple', 'orange'}
  1. discard(): Removes an item, but does not raise an error if the item is not found.
# Discarding an item from the set
fruits.discard("grape")  # "grape" doesn't exist in the set
print(fruits)

Output:

{'cherry', 'apple', 'orange'}
  1. pop(): Removes a random item from the set. Since sets are unordered, you don’t know which item will be removed.
# Popping a random item from the set
removed_item = fruits.pop()
print(f"Removed item: {removed_item}")
print(fruits)

Output:

Removed item: cherry
{'apple', 'orange'}

Clearing a Set

If you want to remove all items from a set, you can use the clear() method.

# Clearing all items from the set
fruits.clear()
print(fruits)

Output:

set()

Copying a Set

If you want to create a copy of a set (so that changing the copy doesn’t affect the original), you can use the copy() method.

# Copying the set
fruits = {"apple", "banana", "cherry"}
fruits_copy = fruits.copy()
print(fruits_copy)

Output:

{'banana', 'cherry', 'apple'}

Set Operations

Python sets support mathematical set operations like union, intersection, and difference.

Union (|)

The union operation combines two sets and returns all unique elements.

# Union of two sets
set1 = {"apple", "banana"}
set2 = {"banana", "cherry", "date"}
union_set = set1 | set2
print(union_set)

Output:

{'cherry', 'banana', 'apple', 'date'}

Intersection (&)

The intersection operation returns only the items that are common in both sets.

# Intersection of two sets
intersection_set = set1 & set2
print(intersection_set)

Output:

{'banana'}

Difference (-)

The difference operation returns items that are in the first set but not in the second.

# Difference of two sets
difference_set = set1 - set2
print(difference_set)

Output:

{'apple'}

Symmetric Difference (^)

The symmetric difference returns items that are in either of the sets, but not in both.

# Symmetric difference of two sets
sym_diff_set = set1 ^ set2
print(sym_diff_set)

Output:

{'cherry', 'apple', 'date'}

Set Length

You can find the number of items in a set using the len() function.

# Getting the length of a set
set_length = len(fruits)
print(set_length)

Output:

3

Checking if an Item Exists in a Set

You can check if an item is in a set using the in keyword.

# Checking if an item exists in the set
is_apple_present = "apple" in fruits
print(is_apple_present)

Output:

True
< Sets
String Methods >