Static Python

Hi. I am trying to create a class that will allow only one instance of itself to be created. I was looking for something like static(in c++) for python. Is there something like this? Thanks!

What you want to do is to implement the Singleton pattern. You'll want to look at the Overriding the __new__ method section of Unifying types and classes. I've linked directly to the specific section where implementation is discussed but I recommend reading the entire essay.

There are several ways to create singletons in Python, and they are covered in depth in the Python Cookbook on ASPN.

http://aspn.activestate.com/ASPN/Co...on/Recipe/52558
http://aspn.activestate.com/ASPN/Co...on/Recipe/66531
http://aspn.activestate.com/ASPN/Co...on/Recipe/66531
http://aspn.activestate.com/ASPN/Co...n/Recipe/102187

Some of them use deep Python magic, such as metaclasses.

However the simplest way to create a singleton is to just use a module instead of a class. It is not as powerful as a class singleton since you can't use inheritance, but 99% of the time you don't need to.

I generally avoid singletons since they tend to increase coupling between classes and make unit testing harder.

Dave - The Developers' Coach