===== Constructor =====

===== Decorator =====

===== Null object =====

===== Observer =====

===== Proxy =====

===== Singleton =====

Aka Borg pattern

<code python>

class Singleton:
    __shared_state = {}
    def __init__(self):
        self.__dict__ = self.__shared_state

s1 = Singleton()
s1.x = 1
s2 = Singleton()
s2.x # 1
</code>