Python函数作为一等公民详解

def greet(name):
    return f"Hello, {name}!"
say_hello = greet  # 把函数对象赋给变量
print(say_hello("Alice"))  # 输出：Hello, Alice!

numbers = [1, 2, 3, 4]
squared = list(map(lambda x: x ** 2, numbers))  # lambda 是函数，传给了 map
def is_even(x): return x % 2 == 0
evens = list(filter(is_even, numbers))  # 自定义函数传入 filter

def make_multiplier(n):
    def multiplier(x):
        return x * n
    return multiplier  # 返回函数对象，不加括号
double = make_multiplier(2)
triple = make_multiplier(3)
print(double(5))   # 10
print(triple(5))   # 15

operations = {
    "add": lambda a, b: a + b,
    "sub": lambda a, b: a - b,
    "mul": lambda a, b: a * b
}
print(operations["add"](10, 3))  # 13
print(operations["mul"](4, 7))   # 28