class Singleton:
    _instance = None
def __new__(cls):
    if cls._instance is None:
        cls._instance = super().__new__(cls)
    return cls._instance
使用示例
s1 = Singleton()
s2 = Singleton()
print(s1 is s2)  # 输出: True

class CSVParser:
    def parse(self, data):
        return f"解析CSV数据: {data}"
class JSONParser:
def parse(self, data):
return f"解析JSON数据: {data}"
class ParserFactory:
@staticmethod
def get_parser(file_type):
if file_type == "csv":
return CSVParser()
elif file_type == "json":
return JSONParser()
else:
raise ValueError("不支持的文件类型")
使用示例
factory = ParserFactory()
parser = factory.get_parser("json")
print(parser.parse("用户信息"))

class Subject:
    def __init__(self):
        self._observers = []
def attach(self, observer):
    self._observers.append(observer)

def notify(self, message):
    for observer in self._observers:
        observer.update(message)
class Observer:
def update(self, message):
print(f"收到通知: {message}")
使用示例
subject = Subject()
observer_a = Observer()
observer_b = Observer()
subject.attach(observer_a)
subject.attach(observer_b)
subject.notify("系统更新了！")

def log_call(func):
    def wrapper(*args, **kwargs):
        print(f"调用函数: {func.__name__}")
        return func(*args, **kwargs)
    return wrapper
@log_call
def greet(name):
print(f"你好, {name}")
greet("小明")