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    <p>This is what I might do:</p> <pre><code>class SuperClass(object): def __init__(self): if type(self) == SuperClass: raise Exception("&lt;SuperClass&gt; must be subclassed.") # assert(type(self) == SuperClass) class SubClass(SuperClass): def __init__(self): SuperClass.__init__(self) subC = SubClassOne() supC = SuperClass() # This line should throw an exception </code></pre> <p>When run (exception is thrown!):</p> <pre><code>[ 18:32 jon@hozbox ~/so/python ]$ ./preventing-direct-instantiation.py Traceback (most recent call last): File "./preventing-direct-instantiation.py", line 15, in &lt;module&gt; supC = SuperClass() File "./preventing-direct-instantiation.py", line 7, in __init__ raise Exception("&lt;SuperClass&gt; must be subclassed.") Exception: &lt;SuperClass&gt; must be subclassed. </code></pre> <hr> <p>Edit (from comments):</p> <pre><code>[ 20:13 jon@hozbox ~/SO/python ]$ cat preventing-direct-instantiation.py #!/usr/bin/python class SuperClass(object): def __init__(self): if type(self) == SuperClass: raise Exception("&lt;SuperClass&gt; must be subclassed.") class SubClassOne(SuperClass): def __init__(self): SuperClass.__init__(self) class SubSubClass(SubClassOne): def __init__(self): SubClassOne.__init__(self) class SubClassTwo(SubClassOne, SuperClass): def __init__(self): SubClassOne.__init__(self) SuperClass.__init__(self) subC = SubClassOne() try: supC = SuperClass() except Exception, e: print "FAILED: supC = SuperClass() - %s" % e else: print "SUCCESS: supC = SuperClass()" try: subSubC = SubSubClass() except Exception, e: print "FAILED: subSubC = SubSubClass() - %s" % e else: print "SUCCESS: subSubC = SubSubClass()" try: subC2 = SubClassTwo() except Exception, e: print "FAILED: subC2 = SubClassTwo() - %s" % e else: print "SUCCESS: subC2 = SubClassTwo()" </code></pre> <p>Prints:</p> <pre><code>[ 20:12 jon@hozbox ~/SO/python ]$ ./preventing-direct-instantiation.py FAILED: supC = SuperClass() - &lt;SuperClass&gt; must be subclassed. SUCCESS: subSubC = SubSubClass() SUCCESS: subC2 = SubClassTwo() </code></pre>
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    1. POPreventing a class from direct instantiation in Python
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    1. CONot saying this isn't pretty cool, but I think it shows exactly why you shouldn't try to do this sort of thing. I'm pretty sure both examples fail with multiple inheritance.
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    2. CO@sdolan I just tested, and it actually worked with `class SubSubClass(SubClassOne):` and calling `SubClassOne.__init__(self)` from its `__init__`!
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    3. COAhh very cool. Thanks for making that update.
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