Using Frozenset as Dictionary Keys or for Immutable Sets

# Problem: Regular sets are mutable and cannot be used as dictionary keys
# my_set = {'a', 'b'}
# my_dict = {my_set: 'value'} # This would raise a TypeError: unhashable type: 'set'

# Solution: Use frozenset for immutable (hashable) sets
permissions_level_1 = frozenset({'read', 'write'})
permissions_level_2 = frozenset({'read', 'write', 'delete'})
permissions_level_3 = frozenset({'admin'})

# frozenset can be used as a dictionary key
role_access = {
    permissions_level_1: "Standard User",
    permissions_level_2: "Power User",
    permissions_level_3: "Administrator"
}

print(f"Access for {'read', 'write'}: {role_access[frozenset({'read', 'write'})]}")
# Output: Access for {'read', 'write'}: Standard User

# frozenset can also be an element of another set
all_permission_sets = {permissions_level_1, permissions_level_3}
print(f"All defined permission sets: {all_permission_sets}")
# Output: All defined permission sets: {frozenset({'read', 'write'}), frozenset({'admin'})}

# Example: Grouping data by unique combinations of tags
products_with_tags = [
    {"name": "Chair", "tags": frozenset({"furniture", "home")}},
    {"name": "Desk", "tags": frozenset({"furniture", "office")}},
    {"name": "Lamp", "tags": frozenset({"home", "lighting")}},
    {"name": "Bookshelf", "tags": frozenset({"home", "furniture")}},
]

# Group products by their exact tag combination
products_by_tags = {}
for product in products_with_tags:
    tags = product["tags"]
    if tags not in products_by_tags:
        products_by_tags[tags] = []
    products_by_tags[tags].append(product["name"])

print("
Products grouped by tags:")
for tags, names in products_by_tags.items():
    print(f"{sorted(list(tags))}: {names}")
# Output:
# ['furniture', 'home']: ['Chair', 'Bookshelf']
# ['furniture', 'office']: ['Desk']
# ['home', 'lighting']: ['Lamp']