s = {'a', 'b', 'c', 'd', 'e', 'f'}
print(s)  # 每次輸出順序可能不同，例如: {'c', 'a', 'f', 'd', 'b', 'e'}

s = {1, 2, 3, 2, 1, 4, 3}
print(s)  # 輸出: {1, 2, 3, 4} - 自動去重了！

# 這些可以：
s1 = {1, 2, 3}                    # 整數(shù)
s2 = {'a', 'b', 'c'}               # 字符串
s3 = {(1, 2), (3, 4)}              # 元組（元素都是不可變的）

# 這些會報錯：
s4 = {[1, 2], [3, 4]}              # ? TypeError: unhashable type: 'list'
s5 = {{'a': 1}}                    # ? TypeError: unhashable type: 'dict'
s6 = {{1, 2}}                      # ? TypeError: unhashable type: 'set'

# 基本創(chuàng)建
fruits = {"apple", "banana", "orange"}
print(fruits)  # {'banana', 'orange', 'apple'}

# 數(shù)字集合
numbers = {1, 2, 3, 4, 5}
print(numbers)  # {1, 2, 3, 4, 5}

# 混合類型（只要是不可變類型就行）
mixed = {"hello", 123, (1, 2, 3)}
print(mixed)  # {'hello', 123, (1, 2, 3)}

s = {1, 2, 3, 2, 1, 4, 3}
print(s)  # {1, 2, 3, 4} - 自動去重了！

# ? 這是字典，不是集合！
empty_dict = {}
print(type(empty_dict))  # <class 'dict'>

# ? 這才是空集合
empty_set = set()
print(type(empty_set))  # <class 'set'>
print(empty_set)  # set()

empty_set = set()
print(empty_set)  # set()

# 從列表創(chuàng)建（自動去重）
lst = [1, 2, 3, 2, 1, 4]
s1 = set(lst)
print(s1)  # {1, 2, 3, 4}

# 從元組創(chuàng)建
tup = (1, 2, 3, 2, 1)
s2 = set(tup)
print(s2)  # {1, 2, 3}

# 從字符串創(chuàng)建（把字符拆成集合，自動去重）
text = "hello"
s3 = set(text)
print(s3)  # {'h', 'e', 'l', 'o'} - 注意 'l' 只出現(xiàn)一次

original = {1, 2, 3}
copied = set(original)
print(copied)  # {1, 2, 3}

# 基本語法
squares = {x**2 for x in range(1, 6)}
print(squares)  # {16, 1, 4, 9, 25}

# 帶條件篩選
even_squares = {x**2 for x in range(1, 10) if x % 2 == 0}
print(even_squares)  # {16, 4, 36, 64}

# 從字符串過濾
text = "hello world"
unique_vowels = {char for char in text if char in 'aeiou'}
print(unique_vowels)  # {'e', 'o'}

# 復(fù)雜一點的條件
pairs = {(x, y) for x in range(3) for y in range(3)}
print(pairs)  # {(0, 0), (0, 1), (0, 2), (1, 0), ...}

fruits = {"apple", "banana", "orange"}

# 用 for 循環(huán)遍歷
for fruit in fruits:
    print(fruit)  # 每次順序可能不同

fruits = {"apple", "banana", "orange"}

print("apple" in fruits)    # True
print("grape" in fruits)   # False

s = {1, 2, 3}
s.add(4)
print(s)  # {1, 2, 3, 4}

# 如果添加已存在的元素，什么都不會發(fā)生（自動去重）
s.add(2)
print(s)  # {1, 2, 3, 4} - 2 已經(jīng)在集合里了

s = {1, 2, 3}
s.update([4, 5, 6])       # 從列表添加
print(s)  # {1, 2, 3, 4, 5, 6}

s.update((7, 8))          # 從元組添加
print(s)  # {1, 2, 3, 4, 5, 6, 7, 8}

s.update({9, 10})         # 從集合添加
print(s)  # {1, 2, 3, 4, 5, 6, 7, 8, 9, 10}

s.update("hello")         # 從字符串添加（每個字符）
print(s)  # {1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 'h', 'e', 'l', 'o'}

s = {1, 2, 3, 4, 5}
s.remove(3)
print(s)  # {1, 2, 4, 5}

# 如果元素不存在，會拋出 KeyError
s.remove(100)  # KeyError: 100

s = {1, 2, 3, 4, 5}
s.discard(3)
print(s)  # {1, 2, 4, 5}

# 元素不存在也不會報錯，安全感滿滿！
s.discard(100)  # 什么都不發(fā)生，程序繼續(xù)運行

s = {1, 2, 3, 4, 5}
removed = s.pop()
print(f"刪除的元素: {removed}")  # 隨機(jī)一個元素
print(f"剩余集合: {s}")

# 空集合調(diào)用 pop() 會報錯
empty_set = set()
empty_set.pop()  # KeyError: 'pop from an empty set'

s = {1, 2, 3, 4, 5}
s.clear()
print(s)  # set() - 變成空集合了

s = {1, 2, 3, 4, 5}
print(len(s))  # 5

# 自動去重，所以長度會變
s = {1, 1, 1, 2, 2, 3}
print(len(s))  # 3

set1 = {1, 2, 3}
set2 = {3, 4, 5}

# 用 | 運算符
result = set1 | set2
print(result)  # {1, 2, 3, 4, 5}

set1 = {1, 2, 3}
set2 = {3, 4, 5}

# 用 union() 方法
result = set1.union(set2)
print(result)  # {1, 2, 3, 4, 5}

# union() 可以接收多個參數(shù)
result = set1.union(set2, {6, 7})
print(result)  # {1, 2, 3, 4, 5, 6, 7}

set1 = {1, 2, 3}
set2 = {3, 4, 5}

# 用 & 運算符
result = set1 & set2
print(result)  # {3}

set1 = {1, 2, 3}
set2 = {3, 4, 5}

# 用 intersection() 方法
result = set1.intersection(set2)
print(result)  # {3}

# intersection() 可以接收多個參數(shù)
set3 = {3, 5, 6}
result = set1.intersection(set2, set3)
print(result)  # {3}

set1 = {1, 2, 3}
set2 = {3, 4, 5}

# 用 - 運算符
result = set1 - set2
print(result)  # {1, 2}

# 注意順序：set2 - set1 結(jié)果不同
result = set2 - set1
print(result)  # {4, 5}

set1 = {1, 2, 3}
set2 = {3, 4, 5}

# 用 difference() 方法
result = set1.difference(set2)
print(result)  # {1, 2}

set1 = {1, 2, 3}
set2 = {3, 4, 5}

# 用 ^ 運算符
result = set1 ^ set2
print(result)  # {1, 2, 4, 5}

set1 = {1, 2, 3}
set2 = {3, 4, 5}

# 用 symmetric_difference() 方法
result = set1.symmetric_difference(set2)
print(result)  # {1, 2, 4, 5}

A = {1, 2, 3}
B = {1, 2, 3, 4, 5}

# 用 <= 判斷 A 是否是 B 的子集
print(A <= B)           # True
print(A.issubset(B))   # True

# 用 < 判斷 A 是否是 B 的真子集（不是相等的情況）
print(A < B)            # True
print(A == B)          # False

A = {1, 2, 3, 4, 5}
B = {1, 2, 3}

# 用 >= 判斷 A 是否是 B 的超集
print(A >= B)           # True
print(A.issuperset(B)) # True

# 用 > 判斷 A 是否是 B 的真超集
print(A > B)            # True
print(A == B)          # False

s1 = {1, 2, 3, 4}
s2 = {3, 4, 5, 6}

# 求交集，并原地修改 s1
s1.intersection_update(s2)
print(s1)  # {3, 4}

s1 = {1, 2, 3, 4}
s2 = {3, 4, 5, 6}

# 求差集，并原地修改 s1
s1.difference_update(s2)
print(s1)  # {1, 2}

s1 = {1, 2, 3, 4}
s2 = {3, 4, 5, 6}

# 求對稱差集，并原地修改 s1
s1.symmetric_difference_update(s2)
print(s1)  # {1, 2, 5, 6}

s1 = {1, 2, 3}
s2 = {3, 4, 5}

# 求并集，并原地修改 s1
s1.update(s2)
print(s1)  # {1, 2, 3, 4, 5}

lst = [1, 2, 3, 2, 1, 4, 3]
unique = list(set(lst))
print(unique)  # [1, 2, 3, 4] - 無序

# 如果需要保持順序，用 dict.fromkeys()
# 原理：Python 3.7+ 字典保持插入順序，我們利用鍵的唯一性來去重
unique_ordered = list(dict.fromkeys(lst))
print(unique_ordered)  # [1, 2, 3, 4]

text = "hello world"
unique_chars = set(text)
print(unique_chars)  # {'h', 'e', 'l', 'o', ' ', 'w', 'r', 'd'}

# 按原順序 - 利用字典鍵的唯一性和保持順序的特性
unique_ordered = ''.join(dict.fromkeys(text))
print(unique_ordered)  # helo wrd

data = [{'a': 1}, {'b': 2}, {'a': 1}, {'b': 2}]
unique = list(dict.fromkeys(data))
print(unique)  # [{'a': 1}, {'b': 2}]

# 從可迭代對象創(chuàng)建
fs1 = frozenset([1, 2, 3, 4, 5])
print(fs1)  # frozenset({1, 2, 3, 4, 5})

# 從字符串創(chuàng)建
fs2 = frozenset("hello")
print(fs2)  # frozenset({'h', 'e', 'l', 'o'})

# 從集合創(chuàng)建
fs3 = frozenset({1, 2, 3})
print(fs3)  # frozenset({1, 2, 3})

# 用 frozenset 作為字典的鍵
favorites = {
    frozenset(['apple', 'banana']): '水果',
    frozenset(['chicken', 'beef']): '肉類'
}
print(favorites)  # {frozenset({'apple', 'banana'}): '水果', ...}

# 集合的集合 - 普通 set 不行
set_of_sets = {frozenset([1, 2]), frozenset([3, 4])}
print(set_of_sets)  # {frozenset({1, 2}), frozenset({3, 4})}

fs = frozenset([1, 2, 3])
print(hash(fs))  # 可以哈希

s = {1, 2, 3}
# print(hash(s))  # TypeError: unhashable type: 'set'