一文详解Python函数定义的12个参数传递技巧

def greet(name):  # 定义一个函数，接收一个参数name
    print(f"Hello, {name}!")  # 打印问候语

greet("Alice")  # 调用函数，传入参数"Alice"

def add(a, b):  # 定义一个加法函数
    return a + b  # 返回两个数的和

result = add(3, 5)  # 调用函数并接收返回值
print(result)  # 输出结果

def greet(name, age):
    """打印名字和年龄"""
    print(f"Hello, {name}. You are {age} years old.")

greet("Alice", 25)  # 输出: Hello, Alice. You are 25 years old.

greet(age=30, name="Bob")  # 输出: Hello, Bob. You are 30 years old.

greet("Charlie")  # 报错：缺少参数age

def greet(name, greeting="Hello"):
    # 如果没有传入greeting，默认使用"Hello"
    return f"{greeting}, {name}!"

print(greet("Alice"))  # 输出: Hello, Alice!
print(greet("Bob", "Hi"))  # 输出: Hi, Bob!

def add_item(item, items=[]):  # 默认值items是空列表
    items.append(item)
    return items

print(add_item(1))  # 输出: [1]
print(add_item(2))  # 输出: [1, 2]！并不是预期的[2]

def add_item(item, items=None):
    if items is None:  # 每次调用都创建新的列表
        items = []
    items.append(item)
    return items

print(add_item(1))  # 输出: [1]
print(add_item(2))  # 输出: [2]，符合预期

def greet(name, greeting="Hello"):
    print(f"{greeting}, {name}!")

# 使用关键字参数调用
greet(name="Alice", greeting="Hi")  # 输出：Hi, Alice!

def info(age, name):
    print(f"{name} is {age} years old.")

# 混淆顺序时，使用关键字参数避免错误
info(name="Bob", age=25)  # 输出：Bob is 25 years old.

def multiply(x, y, factor=1):
    return x * y * factor

result = multiply(3, 5, factor=2)  # 输出：30
print(result)

def sum_numbers(*args):  # *args 收集所有位置参数
    return sum(args)      # 计算元组中所有数字的和

result = sum_numbers(1, 2, 3, 4)
print(result)  # 输出：10

def greet(name, *args):
    message = f"Hello, {name}!"
    for arg in args:
        message += f" And hello to you too, {arg}!"
    return message

print(greet("Alice", "Bob", "Charlie"))
# 输出：Hello, Alice! And hello to you too, Bob! And hello to you too, Charlie!

def greet(**kwargs):
    for key, value in kwargs.items():
        print(f"{key}: {value}")

# 调用函数
greet(name="Alice", age=25, city="Beijing")

def create_html_tag(tag_name, content, **attributes):
    # 构建属性部分
    attr_str = ' '.join([f'{k}="{v}"' for k, v in attributes.items()])
    return f"<{tag_name} {attr_str}>{content}</{tag_name}>"

# 使用示例
html = create_html_tag("a", "Click me!", href="https://example.com" rel="external nofollow"  rel="external nofollow" , target="_blank")
print(html)

# 定义一个函数
def my_function(a, b, c):
    print(f"a={a}, b={b}, c={c}")

# 列表解包
my_list = [1, 2, 3]
my_function(*my_list)  # 输出: a=1, b=2, c=3

# 字典解包
my_dict = {'a': 4, 'b': 5, 'c': 6}
my_function(**my_dict)  # 输出: a=4, b=5, c=6

def another_function(*args, **kwargs):
    print("Positional arguments:", args)
    print("Keyword arguments:", kwargs)

# 使用解包传递参数
another_function(*[7, 8], **{'key': 'value'})
# 输出:
# Positional arguments: (7, 8)
# Keyword arguments: {'key': 'value'}

global_var = 10  # 全局变量

def my_function(local_var):
    print(f"局部变量: {local_var}")  # 访问局部变量
    print(f"全局变量: {global_var}")  # 访问全局变量

my_function(5)  # 调用函数并传递局部变量

count = 0  # 定义全局变量

def increment():
    global count  # 声明使用全局变量
    count += 1
    print(f"当前计数: {count}")

increment()  # 调用函数
increment()

add = lambda x, y: x + y  # 定义一个简单的加法函数
print(add(3, 5))  # 输出结果为8

# 按字符串长度排序
words = ["apple", "banana", "cherry", "date"]
sorted_words = sorted(words, key=lambda word: len(word))
print(sorted_words)  # 输出['date', 'apple', 'banana', 'cherry']

# 过滤出偶数
numbers = [1, 2, 3, 4, 5, 6]
even_numbers = list(filter(lambda x: x % 2 == 0, numbers))
print(even_numbers)  # 输出[2, 4, 6]

def my_decorator(func):
    def wrapper(*args, **kwargs):  # 使用通用参数接收
        print("Before function call")
        result = func(*args, **kwargs)
        print("After function call")
        return result
    return wrapper

@my_decorator
def greet(name):
    print(f"Hello, {name}!")

greet("Alice")  # 输出：Before function call\nHello, Alice!\nAfter function call

from functools import wraps

def my_decorator(func):
    @wraps(func)  # 保留原函数的元信息
    def wrapper(*args, **kwargs):
        print("Before function call")
        return func(*args, **kwargs)
    return wrapper

@my_decorator
def greet(name):
    """Greet someone by name."""
    print(f"Hello, {name}!")

print(greet.__name__)  # 输出：greet
print(greet.__doc__)   # 输出：Greet someone by name.

def calculate_price(item, *, tax_rate, discount):
    """计算商品价格（包含税率和折扣）"""
    price = item['price']
    taxed_price = price * (1 + tax_rate)
    final_price = taxed_price * (1 - discount)
    return final_price

# 调用函数时必须指定参数名称
item = {'price': 100}
result = calculate_price(item, tax_rate=0.1, discount=0.2)
print(result)  # 输出：88.0

def add_numbers(a: int, b: int) -> int:
    return a + b

result = add_numbers(5, 10)  # 正确用法
print(result)  # 输出：15

def divide(a: float, b: float) -> float:
    assert b != 0, "除数不能为零"
    return a / b

print(divide(10, 2))  # 输出：5.0
# print(divide(10, 0))  # 触发断言错误

def log_message(message, *, level="INFO", **kwargs):
    """
    日志记录函数，支持多种输入格式。
    :param message: 要记录的日志信息（可以是字符串、字典或列表）
    :param level: 日志级别，默认为 "INFO"
    :param kwargs: 其他可选参数
    """
    timestamp = kwargs.get("timestamp", "N/A")  # 获取时间戳，默认为 "N/A"
    if isinstance(message, str):  # 如果是字符串
        formatted_message = f"[{level}] [{timestamp}] {message}"
    elif isinstance(message, dict):  # 如果是字典
        formatted_message = f"[{level}] [{timestamp}] {dict(message)}"
    elif isinstance(message, list):  # 如果是列表
        formatted_message = f"[{level}] [{timestamp}] {list(message)}"
    else:
        formatted_message = f"[{level}] [{timestamp}] Unsupported type: {type(message)}"

    print(formatted_message)  # 输出日志

# 测试代码
log_message("This is a test log.")  # 字符串输入
log_message({"key": "value"}, level="DEBUG", timestamp="2023-03-01 12:00:00")  # 字典输入
log_message([1, 2, 3], level="WARNING")  # 列表输入