Python——23种设计模式

单例模式：

为了确保在单例模式下，创建的每一个线程都是在同一块内存空间中，这样做的目的就是为了节省重复性的线程所导致的占用内存空间。

不加单例模式的实例化效果：

class SingLeton(object):
    pass
 
obj1 = SingLeton()
print(obj1)  #<__main__.SingLeton object at 0x00000167A41C7700>
obj2 = SingLeton()
print(obj2)   #<__main__.SingLeton object at 0x00000167A41C7C10>

使用单例模式后：

class SingLeton(object):
    instance = None
    def __new__(cls, *args, **kwargs):
        if not cls.instance:
            cls.instance = object.__new__(cls)
        return cls.instance
obj1 = SingLeton()
print(obj1)   #<__main__.SingLeton object at 0x00000167B0277C10>
obj2 = SingLeton()
print(obj2)   #<__main__.SingLeton object at 0x00000167B0277C10>

线程+锁的单例模式

from threading import Thread,Lock
 
class SingLeton(object):
    instance = None
    lock = Lock()
    def __new__(cls, *args, **kwargs):
        with cls.lock:
            if not cls.instance:
                cls.instance = object.__new__(cls)
        return cls.instance
for i in range(10):
    print(SingLeton())