# 函数定义示例

# 定义简单的函数
def greet():
    """这是一个简单的问候函数"""
    print("你好！欢迎学习Python函数。")

# 调用函数
greet()

# 带参数的函数
def greet_person(name):
    """向指定的人问候"""
    print(f"你好，{name}！")

greet_person("小明")
greet_person("小红")

# 带返回值的函数
def add_numbers(a, b):
    """返回两个数的和"""
    return a + b

result = add_numbers(5, 3)
print(f"5 + 3 = {result}")

# 带默认参数的函数
def power(base, exponent=2):
    """计算幂，默认指数为2（平方）"""
    return base ** exponent

print(f"3的平方: {power(3)}")
print(f"2的3次方: {power(2, 3)}")

# 关键字参数
def create_person(name, age, city):
    """创建人员信息"""
    return f"姓名: {name}, 年龄: {age}, 城市: {city}"

# 使用关键字参数，可以不按顺序
person1 = create_person(age=20, city="北京", name="张三")
print(person1)

# 可变数量参数
def calculate_average(*numbers):
    """计算任意数量数字的平均值"""
    if len(numbers) == 0:
        return 0
    return sum(numbers) / len(numbers)

avg1 = calculate_average(1, 2, 3, 4, 5)
avg2 = calculate_average(10, 20, 30)
print(f"平均值1: {avg1}")
print(f"平均值2: {avg2}")

# 返回多个值
def get_min_max(numbers):
    """返回列表中的最小值和最大值"""
    if not numbers:
        return None, None
    return min(numbers), max(numbers)

scores = [85, 92, 78, 90, 88]
lowest, highest = get_min_max(scores)
print(f"最低分: {lowest}, 最高分: {highest}")

# 函数嵌套
def outer_function(x):
    """外层函数"""
    def inner_function(y):
        """内层函数"""
        return y * 2
    return inner_function(x) + 10

result = outer_function(5)
print(f"函数嵌套结果: {result}")

# lambda表达式（匿名函数）
square = lambda x: x ** 2
print(f"5的平方(lambda): {square(5)}")

# 使用lambda进行排序
students = [
    {"name": "小明", "score": 85},
    {"name": "小红", "score": 92},
    {"name": "小刚", "score": 78}
]

# 按成绩排序
students_sorted = sorted(students, key=lambda s: s["score"], reverse=True)
print("\n按成绩排序:")
for student in students_sorted:
    print(f"  {student['name']}: {student['score']}")