# 传统方式
squares = []
for x in range(10):
    squares.append(x**2)

# 列表推导式
squares = [x**2 for x in range(10)]

# 带条件的列表推导式
even_squares = [x**2 for x in range(10) if x % 2 == 0]

# 字典推导式
square_dict = {x: x**2 for x in range(5)}
# 输出: {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

# 集合推导式
unique_lengths = {len(word) for word in ['apple', 'banana', 'cherry']}
# 输出: {5, 6}

# 定义一个简单的装饰器
def my_decorator(func):
    def wrapper():
        print("函数执行前")
        func()
        print("函数执行后")
    return wrapper

# 使用装饰器
@my_decorator
def say_hello():
    print("Hello!")

say_hello()
# 输出:
# 函数执行前
# Hello!
# 函数执行后

# 传统文件操作
file = open('example.txt', 'r')
try:
    content = file.read()
finally:
    file.close()

# 使用with语句
with open('example.txt', 'r') as file:
    content = file.read()
# 文件会自动关闭

# 函数参数解包
def my_func(a, b, c):
    return a + b + c

args = [1, 2, 3]
result = my_func(*args)  # 相当于 my_func(1, 2, 3)

# 字典解包
kwargs = {'a': 1, 'b': 2, 'c': 3}
result = my_func(**kwargs)  # 相当于 my_func(a=1, b=2, c=3)

# 合并字典
dict1 = {'a': 1, 'b': 2}
dict2 = {'c': 3, 'd': 4}
merged = {**dict1, **dict2}  # {'a': 1, 'b': 2, 'c': 3, 'd': 4}

# 传统方式
n = len(my_list)
if n > 10:
    print(f"列表过长: {n} 个元素")

# 使用海象运算符
if (n := len(my_list)) > 10:
    print(f"列表过长: {n} 个元素")

# 在列表推导式中使用
results = [result for line in lines if (result := process(line)) is not None]