This is one simple way to emulate a singleton class on behalf of a normal class. (A singleton class is a class with at most one instance.)
The implementation does not emulate a class 100% (for example it lacks the special attributes lile __dict__ or __bases__), but it should be absolutely sufficient in most common cases.
def Singleton(cls):
instance = []
def create(*args, **kw):
if not instance:
instance.append(cls(*args, **kw))
return instance[0]
return create
# Test:
TheList = Singleton(list)
def test2():
mylist1 = TheList([1,2,3])
mylist2 = TheList()
print mylist1, mylist2
mylist1.append(4)
del mylist1[1]
print mylist1, mylist2
>>> test2()
[1, 2, 3] [1, 2, 3]
[1, 3, 4] [1, 3, 4]We're a friendly, industry-focused community of developers, IT pros, digital marketers, and technology enthusiasts meeting, networking, learning, and sharing knowledge.