一文掌握Python函数进阶：参数类型与返回值

python
def greet(name, message):
    print(f"{message}, {name}!")
greet("Alice", "Hello")   # Hello, Alice!
greet("Bob")              # TypeError: missing 1 required positional argument

python
def greet(name, message="Hello"):
    print(f"{message}, {name}!")
greet("Alice")           # Hello, Alice!
greet("Bob", "Hi")       # Hi, Bob!

python
def add_item(item, lst=[]):   # 不推荐
    lst.append(item)
    return lst
print(add_item(1))   # [1]
print(add_item(2))   # [1, 2]  共享了同一个列表！
# 推荐写法
def add_item(item, lst=None):
    if lst is None:
        lst = []
    lst.append(item)
    return lst

python
def sum_all(*args):
    return sum(args)
print(sum_all(1, 2, 3, 4))   # 10
print(sum_all())             # 0

python
def describe_person(name, age, city):
    print(f"{name} is {age} years old and lives in {city}.")
describe_person("Alice", city="New York", age=25)   # 合法

python
def print_info(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")
print_info(name="Alice", age=25, city="New York")

python
def complex_func(a, b=1, *args, c, d=2, **kwargs):
    print(f"a={a}, b={b}, args={args}, c={c}, d={d}, kwargs={kwargs}")
complex_func(10, 20, 30, 40, c=50, d=60, e=70, f=80)
# a=10, b=20, args=(30, 40), c=50, d=60, kwargs={'e': 70, 'f': 80}

python
def modify(x, lst):
    x += 1          # 不可变对象，x指向新对象
    lst.append(4)   # 可变对象，原列表被修改
a = 10
b = [1,2,3]
modify(a, b)
print(a)    # 10
print(b)    # [1,2,3,4]

python
def add(a, b, c):
    return a + b + c
nums = [1, 2, 3]
print(add(*nums))          # 6
kwargs = {'a': 10, 'b': 20, 'c': 30}
print(add(**kwargs))       # 60

python
def square(x):
    return x ** 2
result = square(5)   # 25

python
def get_stats(numbers):
    return min(numbers), max(numbers), sum(numbers) / len(numbers)
min_val, max_val, avg = get_stats([1, 2, 3, 4, 5])
print(min_val, max_val, avg)   # 1 5 3.0

python
def make_multiplier(n):
    def multiplier(x):
        return x * n
    return multiplier
times2 = make_multiplier(2)
times3 = make_multiplier(3)
print(times2(5))   # 10
print(times3(5))   # 15

python
def count_up_to(n):
    i = 1
    while i <= n:
        yield i
        i += 1
for num in count_up_to(5):
    print(num)   # 1 2 3 4 5

python
def greet(name: str, age: int = 18) -> str:
    return f"{name} is {age} years old."

python
def person_info(name, *, age, city):
    print(f"{name}, {age}, {city}")
person_info("Alice", age=25, city="NYC")   # 正确
# person_info("Alice", 25, "NYC")          # 错误

python
def divide(a: float, b: float) -> float:
    """
    返回 a 除以 b 的结果。
    参数:
        a (float): 被除数
        b (float): 除数
    返回:
        float: 商
    异常:
        ZeroDivisionError: 当 b 为 0 时抛出
    """
    return a / b