How to adapt the Singleton pattern? (Deprecation warning)

Question

Few years ago I found an implementation of the Singleton pattern in Python by Duncan Booth:

class Singleton(object):
    \"\"\"
    Singleton class by Duncan Boo         


        

Answer 1

So based on the answers from @Sven and @Duncan I found a solution which works for me. The problem actually wasn't in the line of the code raising the TypeError, but in the signature of the __new__() method. The call of the object.__new__(cls) shall be without the *args, **kwargs, but they have to remain in the Singleton.__new__() definition. This is the modified Singleton:

class Singleton(object):
    """
    Singleton class by Duncan Booth.
    Multiple object variables refers to the same object.
    http://www.suttoncourtenay.org.uk/duncan/accu/pythonpatterns.html
    """
   _instance = None

    def __new__(cls, *args, **kwargs):
        if not cls._instance:
            cls._instance = super(Singleton, cls).__new__(cls)
        return cls._instance

And this is an example of sub-classing (which was the issue):

class Child(Singleton):  
    def __init__(self,param=None):  
            print param  
            print 'Doing another stuff'  

ch=Child('Some stuff')

I still don't understand why the signature of Child's __init__() has to match to Singleton's `new(), but this solution works.