[python] Creating a singleton in Python

Maybe I missunderstand the singleton pattern but my solution is this simple and pragmatic (pythonic?). This code fullfills two goals

  1. Make the instance of Foo accessiable everywhere (global).
  2. Only one instance of Foo can exist.

This is the code.

#!/usr/bin/env python3

class Foo:
    me = None

    def __init__(self):
        if Foo.me != None:
            raise Exception('Instance of Foo still exists!')

        Foo.me = self


if __name__ == '__main__':
    Foo()
    Foo()

Output

Traceback (most recent call last):
  File "./x.py", line 15, in <module>
    Foo()
  File "./x.py", line 8, in __init__
    raise Exception('Instance of Foo still exists!')
Exception: Instance of Foo still exists!

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