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  One wrinkle of PEP 362 in CPython is callables implemented directly

  in C.&nbsp; Right now there's no good way to generate such signatures

  automatically.&nbsp; That's why we kept __signature__ in the spec, to

  allow implementors to generate signatures by hand for these

  callables.<br>

  <br>

  But the wrinkle gets wrinklier.&nbsp; The problem is, you often can't add

  arbitrary attributes to these objects:<br>

  <blockquote>&gt;&gt;&gt; import os<br>

   &gt;&gt;&gt; os.stat.random_new_attribute = 3<br>

   Traceback (most recent call last):<br>

   &nbsp; File "&lt;stdin&gt;", line 1, in &lt;module&gt;<br>

   AttributeError: 'builtin_function_or_method' object has no

   attribute 'random_new_attribute'<br>

  </blockquote>

  If users are to attach precomputed signatures to callables

  implemented in C, those callables may need to *already* have a

  __signature__ attribute.<br>

  <br>

  <br>

  I've already added __signature__ to PyCFunctionObject in the PEP 362

  patch.&nbsp; This takes care of the vast bulk of such callables.&nbsp; But

  there are a bunch of obscure callable objects in CPython, and I

  suspect some of them may need a __signature__ attribute.<br>

  <br>

  Here's an almost- complete list, listed as their Python type:<br>

  <blockquote>functools.KeyWrapper (result of functools.cmp_to_key)<br>

   weakref.weakref<br>

   method (bound method objects, aka "x = Class(); x.method")<br>

   instancemethod (is this still even used?&nbsp; it's never used in

   trunk)<br>

   operator.itemgetter<br>

   operator.attrgetter<br>

   operator.methodcaller<br>

   _json.Scanner (result of _json.make_scanner)<br>

   _json.Encoder (result of _json.make_encoder)<br>

   _ctypes.DictRemover (I'm not even sure how you can get your hands

   on one of these)<br>

   sqlite3.Connection<br>

  </blockquote>

  I produced this by grepping for "/* tp_call */" and ignoring all of

  them that were set to "0", then creating one of those objects and

  trying (and failing) to set a __signature__ attribute.<br>

  <br>

  There are four more candidates I found with the grep but couldn't

  figure out how to instantiate and test.&nbsp; They have to do with the

  descriptor protocol, aka properties, but the types aren't directly

  exposed by Python.&nbsp; They're all defined in Object/descrobject.c.&nbsp;

  The internal class names are:<br>

  <blockquote>

   method_descriptor<br>

   classmethod_descriptor<br>

   wrapper_descriptor<br>

   method-wrapper (you get one of these out of a

   "wrapper_descriptor")<br>

  </blockquote>

  <br>

  I'm happy to do the work, but I don't have a good sense of which

  callables need a __signature__ attribute.&nbsp; Can someone here tell me

  which ones might need a __signature__ attribute?<br>

  <br>

  <br>

  <i>/arry</i><br>

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