列表（List） #

# 空列表
empty = []
empty = list()

# 带元素
numbers = [1, 2, 3, 4, 5]
strings = ["apple", "banana", "cherry"]
mixed = [1, "hello", 3.14, True, None]

# 嵌套列表
matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# 从其他可迭代对象创建
list_from_string = list("hello")  # ['h', 'e', 'l', 'l', 'o']
list_from_tuple = list((1, 2, 3))  # [1, 2, 3]
list_from_range = list(range(5))   # [0, 1, 2, 3, 4]

# 基本推导式
squares = [x ** 2 for x in range(5)]
# [0, 1, 4, 9, 16]

# 带条件
evens = [x for x in range(10) if x % 2 == 0]
# [0, 2, 4, 6, 8]

fruits = ["apple", "banana", "cherry", "date"]

# 正向索引
print(fruits[0])   # "apple"
print(fruits[2])   # "cherry"

# 反向索引
print(fruits[-1])  # "date"（最后一个）
print(fruits[-2])  # "cherry"（倒数第二个）

# 索引越界
# print(fruits[10])  # IndexError

numbers = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]

# 基本切片
print(numbers[2:5])    # [2, 3, 4]
print(numbers[:3])     # [0, 1, 2]
print(numbers[7:])     # [7, 8, 9]
print(numbers[:])      # 复制整个列表

# 带步长
print(numbers[::2])    # [0, 2, 4, 6, 8]（每隔一个）
print(numbers[1::2])   # [1, 3, 5, 7, 9]（从索引1开始）

# 反向
print(numbers[::-1])   # [9, 8, 7, 6, 5, 4, 3, 2, 1, 0]
print(numbers[8:2:-1]) # [8, 7, 6, 5, 4, 3]

# 负索引切片
print(numbers[-3:])    # [7, 8, 9]
print(numbers[:-3])    # [0, 1, 2, 3, 4, 5, 6]

fruits = ["apple", "banana", "cherry"]

# 修改单个元素
fruits[1] = "blueberry"
print(fruits)  # ['apple', 'blueberry', 'cherry']

# 修改切片
fruits[1:3] = ["blackberry", "coconut"]
print(fruits)  # ['apple', 'blackberry', 'coconut']

fruits = ["apple", "banana"]

# append：末尾添加
fruits.append("cherry")
print(fruits)  # ['apple', 'banana', 'cherry']

# insert：指定位置插入
fruits.insert(1, "blueberry")
print(fruits)  # ['apple', 'blueberry', 'banana', 'cherry']

# extend：添加多个元素
fruits.extend(["date", "elderberry"])
print(fruits)  # ['apple', 'blueberry', 'banana', 'cherry', 'date', 'elderberry']

# 使用 += 
fruits += ["fig", "grape"]

fruits = ["apple", "banana", "cherry", "date", "banana"]

# del：按索引删除
del fruits[1]
print(fruits)  # ['apple', 'cherry', 'date', 'banana']

# pop：弹出并返回
removed = fruits.pop()     # 弹出最后一个
print(removed)  # 'banana'
print(fruits)   # ['apple', 'cherry', 'date']

removed = fruits.pop(1)    # 弹出指定索引
print(removed)  # 'cherry'

# remove：按值删除（只删除第一个）
fruits = ["apple", "banana", "cherry", "banana"]
fruits.remove("banana")
print(fruits)  # ['apple', 'cherry', 'banana']

# clear：清空列表
fruits.clear()
print(fruits)  # []

fruits = ["apple", "banana", "cherry", "banana"]

# index：查找索引
print(fruits.index("cherry"))    # 2
print(fruits.index("banana", 2)) # 3（从索引2开始查找）
# fruits.index("orange")  # ValueError

# count：统计次数
print(fruits.count("banana"))    # 2
print(fruits.count("orange"))    # 0

# in：成员检查
print("apple" in fruits)   # True
print("orange" in fruits)  # False

numbers = [3, 1, 4, 1, 5, 9, 2, 6]

# sort：原地排序
numbers.sort()
print(numbers)  # [1, 1, 2, 3, 4, 5, 6, 9]

# 反向排序
numbers.sort(reverse=True)
print(numbers)  # [9, 6, 5, 4, 3, 2, 1, 1]

# 自定义排序键
words = ["apple", "pie", "banana", "cherry"]
words.sort(key=len)
print(words)  # ['pie', 'apple', 'banana', 'cherry']

# sorted：返回新列表
numbers = [3, 1, 4, 1, 5]
sorted_numbers = sorted(numbers)
print(sorted_numbers)  # [1, 1, 3, 4, 5]
print(numbers)  # [3, 1, 4, 1, 5]（原列表不变）

# reverse：原地反转
numbers = [1, 2, 3, 4, 5]
numbers.reverse()
print(numbers)  # [5, 4, 3, 2, 1]

# reversed：返回迭代器
reversed_numbers = list(reversed(numbers))

# copy：浅拷贝
original = [1, 2, 3]
copied = original.copy()
copied[0] = 10
print(original)  # [1, 2, 3]（不影响原列表）

# 复制的其他方式
copied = original[:]
copied = list(original)

# 浅拷贝的陷阱
original = [[1, 2], [3, 4]]
copied = original.copy()
copied[0][0] = 99
print(original)  # [[99, 2], [3, 4]]（嵌套列表受影响）

# 深拷贝
import copy
copied = copy.deepcopy(original)

a = [1, 2, 3]
b = [4, 5, 6]

# 使用 +
c = a + b
print(c)  # [1, 2, 3, 4, 5, 6]

# 使用 extend
a.extend(b)

# 使用 +=
a += b

# 使用 *
zeros = [0] * 5
print(zeros)  # [0, 0, 0, 0, 0]

# 注意嵌套
matrix = [[0] * 3] * 3  # 三行共享同一列表
matrix[0][0] = 1
print(matrix)  # [[1, 0, 0], [1, 0, 0], [1, 0, 0]]

# 正确方式
matrix = [[0] * 3 for _ in range(3)]

# 相等比较
print([1, 2, 3] == [1, 2, 3])  # True
print([1, 2, 3] == [3, 2, 1])  # False

# 大小比较（字典序）
print([1, 2] < [1, 3])   # True
print([1, 2] < [1, 2, 3])  # True

fruits = ["apple", "banana", "cherry"]

# 遍历元素
for fruit in fruits:
    print(fruit)

# 带索引遍历
for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")

# 索引遍历
for i in range(len(fruits)):
    print(fruits[i])

names = ["Tom", "Jerry", "Alice"]
ages = [25, 30, 28]

for name, age in zip(names, ages):
    print(f"{name}: {age}岁")

# 错误方式
# numbers = [1, 2, 3]
# for n in numbers:
#     if n == 2:
#         numbers.remove(n)  # 可能出问题

# 正确方式1：遍历副本
numbers = [1, 2, 3, 4, 5]
for n in numbers[:]:
    if n % 2 == 0:
        numbers.remove(n)

# 正确方式2：列表推导式
numbers = [1, 2, 3, 4, 5]
numbers = [n for n in numbers if n % 2 != 0]

matrix = [
    [1, 2, 3],
    [4, 5, 6],
    [7, 8, 9]
]

print(matrix[0])     # [1, 2, 3]
print(matrix[0][1])  # 2
print(matrix[2][2])  # 9

matrix = [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

# 方法1：列表推导式
flat = [x for row in matrix for x in row]
print(flat)  # [1, 2, 3, 4, 5, 6, 7, 8, 9]

# 方法2：itertools
import itertools
flat = list(itertools.chain.from_iterable(matrix))

# 方法3：sum
flat = sum(matrix, [])  # 不推荐，效率低

matrix = [[1, 2, 3], [4, 5, 6]]

# 使用zip
transposed = list(zip(*matrix))
print(transposed)  # [(1, 4), (2, 5), (3, 6)]

# 列表推导式
transposed = [[row[i] for row in matrix] for i in range(3)]

stack = []

# 入栈
stack.append(1)
stack.append(2)
stack.append(3)
print(stack)  # [1, 2, 3]

# 出栈
print(stack.pop())  # 3
print(stack.pop())  # 2
print(stack)        # [1]

from collections import deque

queue = deque()

# 入队
queue.append(1)
queue.append(2)
queue.append(3)
print(queue)  # deque([1, 2, 3])

# 出队
print(queue.popleft())  # 1
print(queue.popleft())  # 2
print(queue)            # deque([3])

# 使用列表（效率较低）
queue = [1, 2, 3]
queue.pop(0)  # 从头部删除，效率低