Attempt at a singleton class for Tracker object

TrackerWrapper

class TrackerWrapper:
    class __TrackerWrapper:
        def __init__(self):
            self.tracker = Tracker.SparqlConnection.get(None)
        def __str__(self):
            return repr(self)
    instance = None
    def __init__(self):
        if not TrackerWrapper.instance:
            TrackerWrapper.instance = TrackerWrapper.__TrackerWrapper()
    def __getattr__(self, name):
        return getattr(self.instance, name) # not actually sure if this is necessary, it's code left over from example

# compare to example at http://python-3-patterns-idioms-test.readthedocs.org/en/latest/Singleton.html


In [58]: a = TrackerWrapper()

In [59]: b = TrackerWrapper()

In [60]: c = TrackerWrapper()

In [61]: a
Out[61]: <__main__.TrackerWrapper at 0x7fdcac023dd8>

In [62]: b
Out[62]: <__main__.TrackerWrapper at 0x7fdcac023da0>

In [63]: c
Out[63]: <__main__.TrackerWrapper at 0x7fdcac023d68>

In [65]: print(a)
<__main__.TrackerWrapper object at 0x7fdcac023dd8>

In [66]: print(b)
<__main__.TrackerWrapper object at 0x7fdcac023da0>

In [67]: print(c)
<__main__.TrackerWrapper object at 0x7fdcac023d68>

In [14]: t1 = Tracker.SparqlConnection.get()

In [15]: t2 = Tracker.SparqlConnection.get()

In [16]: t1
Out[16]: <main.TrackerSparqlBackend object at 0x7f4074046990 (TrackerSparqlBackend at 0x2296870)>

In [17]: t2
Out[17]: <main.TrackerSparqlBackend object at 0x7f4074046990 (TrackerSparqlBackend at 0x2296870)>