Sets

empty = set()                   # empty set, note: {} creates an empty dictionary, not a set ​s1 = {1, 2, 3}                  # set literal

s = {1, 2, 3}​print(2 in s)       # True​print(5 not in s)   # True

s = {3, 1, 0, 5}​print("len(s):", len(s))       # 4print("min(s):", min(s))       # 0print("max(s):", max(s))       # 5print("sum(s):", sum(s))       # 9print("sorted(s):", sorted(s)) # [0, 1, 3, 5]​print("any(s):", any(s))       # True (0 is falsy, but others are truthy)print("all(s):", all(s))       # False (because of 0)

s = {1, 2, 3}​s.add(4)               # {1, 2, 3, 4}​s.update([5, 6])       # {1, 2, 3, 4, 5, 6}​s.remove(3)            # removes 3 (error if not found)​s.discard(10)          # safe remove (no error if not found)​val = s.pop()          # removes & returns an arbitrary element​s.clear()              # empty set

a = {1, 2, 3, 4}b = {3, 4, 5, 6}​# unionprint(a.union(b)) # or short hand versionprint(a | b)   # {1,2,3,4,5,6}​# intersectionprint(a.intersection(b))# or short hand versionprint(a & b)   # {3,4}​# differenceprint(a.difference(b))# or short hand versionprint(a - b)   # {1,2}​# symmetric differenceprint(a.symmetric_difference(b))# or short hand versionprint(a ^ b)   # {1,2,5,6}

a = {1, 2}b = {1, 2, 3}​print(a <= b)         # subset → True​print(b >= a)         # superset → True​print(a.issubset(b))  # True​print(b.issuperset(a))# True​# no elements in commonprint(a.isdisjoint({4, 5}))  # True​# Check equality of sets (same elements, order doesn’t matter){1, 2, 3} == {3, 2, 1} # True

# Listset([1, 2, 2, 3])  # {1, 2, 3}​# Tupleset((1, 1, 2))  # {1, 2}​# Stringset("hello")  # {'h', 'e', 'l', 'o'}​# Dictionaryset({'a':1, 'b':2})  # {'a', 'b'}

{expression for item in iterable if condition}

nums = [1, 2, 2, 3, 4, 4, 5]​# ----------------------------------------# Basic transformationsquares = {x**2 for x in nums}print("Squares set:", squares)  # {1, 4, 9, 16, 25}​# ----------------------------------------# Filtering valuesevens = {x for x in nums if x % 2 == 0}print("Even numbers set:", evens)​# ----------------------------------------# Deduplication (automatically handled)duplicates_removed = {x for x in nums}print("Deduped set:", duplicates_removed)​# ----------------------------------------# Strings with set comprehensionword = "comprehension"unique_chars = {ch for ch in word}print("Unique chars:", unique_chars)​# Uppercase vowels onlyvowels_upper = {ch.upper() for ch in word if ch in "aeiou"}print("Uppercase vowels:", vowels_upper)​# ----------------------------------------# Conditional expression inside comprehensionlabels = {("even" if x % 2 == 0 else "odd") for x in nums}print("Even/Odd labels set:", labels)​# ----------------------------------------# Nested set comprehensionpairs = {(x, y) for x in [1, 2] for y in [3, 4]}print("Cartesian product pairs:", pairs)​# ----------------------------------------# Using functionsdef cube(x): return x**3cubes = {cube(x) for x in nums}print("Cubes set:", cubes)​# ----------------------------------------# Real-world example: normalize texttext = "The quick brown fox jumps over the lazy dog"unique_words = {word.lower() for word in text.split()}print("Unique words (lowercased):", unique_words)

# 1. Creating setsa = {1, 2, 3, 4}b = set([3, 4, 5, 6])c = set((4, 5, 6, 7))s = set("hello")        d = set({'x': 1, 'y': 2}) ​print("Sets:", a, b, c, s, d)​# 2. Set operationsprint("\n# Set Operations")print("Union:", a.union(b))                   # a | bprint("Intersection:", a.intersection(b))     # a & bprint("Difference:", a.difference(b))         # a - bprint("Symmetric Difference:", a.symmetric_difference(b))  # a ^ b​# 3. Set methodsprint("\n# Set Methods")a.add(10)print("After add(10):", a)a.update([20, 30])print("After update([20,30]):", a)a.discard(2)print("After discard(2):", a)# a.remove(100)  # would raise KeyError if uncommentedpopped = a.pop()print("After pop():", a, "Popped element:", popped)copy_a = a.copy()print("Copy of a:", copy_a)a.clear()print("After clear():", a)​# 4. Set casting (removing duplicates)lst = [1, 2, 2, 3, 4, 4, 5]unique_lst = list(set(lst))print("\nCasting to set (remove duplicates):", unique_lst)​# 5. Set comparisonsx = {1, 2, 3}y = {1, 2, 3, 4, 5}z = {6, 7}​print("\n# Set Comparisons")print("x <= y (subset):", x <= y)print("x < y (proper subset):", x < y)print("y >= x (superset):", y >= x)print("y > x (proper superset):", y > x)print("x.isdisjoint(z):", x.isdisjoint(z))print("{1,2,3} == {3,2,1}:", {1,2,3} == {3,2,1})