Python Sets

1# Creating an empty set
2empty_set = set()  # Don't use {} (creates empty dict)
3
4# Creating a set with values
5numbers = {1, 2, 3, 4, 5}
6fruits = {"apple", "banana", "orange"}
7
8# Create set from list (removes duplicates)
9numbers_list = [1, 2, 2, 3, 3, 3, 4, 4, 5]
10unique_numbers = set(numbers_list)
11print(unique_numbers)  # {1, 2, 3, 4, 5}
12
13# Create set from string
14chars = set("hello")
15print(chars)  # {'h', 'e', 'l', 'o'}
16
17# Create immutable frozenset
18frozen = frozenset([1, 2, 3])
19# frozen.add(4)  # Error: frozenset is immutable

1# Define two sets
2A = {1, 2, 3, 4, 5}
3B = {4, 5, 6, 7, 8}
4
5# Union (all unique elements from both sets)
6union = A | B  # or A.union(B)
7print(union)  # {1, 2, 3, 4, 5, 6, 7, 8}
8
9# Intersection (elements present in both sets)
10intersection = A & B  # or A.intersection(B)
11print(intersection)  # {4, 5}
12
13# Difference (elements in A but not in B)
14difference = A - B  # or A.difference(B)
15print(difference)  # {1, 2, 3}
16
17# Symmetric difference (elements in either A or B, but not both)
18sym_diff = A ^ B  # or A.symmetric_difference(B)
19print(sym_diff)  # {1, 2, 3, 6, 7, 8}
20
21# Check if one set is subset of another
22C = {1, 2}
23is_subset = C <= A  # True
24is_proper_subset = C < A  # True
25
26# Check if one set is superset of another
27is_superset = A >= C  # True
28is_proper_superset = A > C  # True

1# Create a set
2numbers = {1, 2, 3}
3
4# Add single element
5numbers.add(4)
6print(numbers)  # {1, 2, 3, 4}
7
8# Add multiple elements
9numbers.update([5, 6, 7])
10print(numbers)  # {1, 2, 3, 4, 5, 6, 7}
11
12# Remove element (raises error if not found)
13numbers.remove(7)
14
15# Remove element (no error if not found)
16numbers.discard(8)  # No error
17
18# Remove and return arbitrary element
19popped = numbers.pop()
20
21# Remove all elements
22numbers.clear()
23
24# Check membership
25if 1 in numbers:
26    print("1 is in the set")
27
28# Iterate through set
29for num in numbers:
30    print(num)

1# Remove duplicates from a list
2numbers = [1, 2, 2, 3, 3, 3, 4, 4, 5]
3unique_numbers = list(set(numbers))
4
5# Find common elements
6list1 = [1, 2, 3, 4, 5]
7list2 = [4, 5, 6, 7, 8]
8common = set(list1) & set(list2)
9
10# Find unique words in text
11text = "the quick brown fox jumps over the lazy dog"
12unique_words = set(text.split())
13
14# Track visited items
15visited = set()
16def process_item(item):
17    if item not in visited:
18        visited.add(item)
19        # Process item...
20
21# Set comprehension
22squares = {x**2 for x in range(10)}
23even_squares = {x**2 for x in range(10) if x % 2 == 0}