Get signatures directly from classes

since we switched to signatures,
we no longer need to reach into `Class.__init__`

IPython/core/oinspect.py

@@ -420,7 +420,6 b' class Inspector(Colorable):'
 
         if inspect.isclass(obj):
             header = self.__head('Class constructor information:\n')
-            obj = obj.__init__
         elif (not py3compat.PY3) and type(obj) is types.InstanceType:
             obj = obj.__call__
 
@@ -766,23 +765,28 b' class Inspector(Colorable):'
         # Constructor docstring for classes
         if inspect.isclass(obj):
             out['isclass'] = True
-            # reconstruct the function definition and print it:
+
+            # get the function signature:
+            try:
+                init_def = self._getdef(obj, oname)
+            except AttributeError:
+                init_def = None
+            else:
+                out['init_definition'] = self.format(init_def)
+
+            # get the __init__ docstring
             try:
-                obj_init =  obj.__init__
+                obj_init = obj.__init__
             except AttributeError:
                 init_def = init_ds = None
             else:
-                init_def = self._getdef(obj_init,oname)
                 init_ds  = getdoc(obj_init)
                 # Skip Python's auto-generated docstrings
                 if init_ds == _object_init_docstring:
                     init_ds = None
 
-            if init_def or init_ds:
-                if init_def:
-                    out['init_definition'] = self.format(init_def)
-                if init_ds:
-                    out['init_docstring'] = init_ds
+            if init_ds:
+                out['init_docstring'] = init_ds
 
         # and class docstring for instances:
         else:

IPython/core/tests/test_oinspect.py

@@ -1,27 +1,17 b''
 """Tests for the object inspection functionality.
 """
-#-----------------------------------------------------------------------------
-#  Copyright (C) 2010-2011 The IPython Development Team.
-#
-#  Distributed under the terms of the BSD License.
-#
-#  The full license is in the file COPYING.txt, distributed with this software.
-#-----------------------------------------------------------------------------
 
-#-----------------------------------------------------------------------------
-# Imports
-#-----------------------------------------------------------------------------
+# Copyright (c) IPython Development Team.
+# Distributed under the terms of the Modified BSD License.
+
 from __future__ import print_function
 
-# Stdlib imports
 import os
 import re
 import sys
 
-# Third-party imports
 import nose.tools as nt
 
-# Our own imports
 from .. import oinspect
 from IPython.core.magic import (Magics, magics_class, line_magic,
                                 cell_magic, line_cell_magic,
@@ -32,6 +22,7 b' from IPython.testing.decorators import skipif'
 from IPython.testing.tools import AssertPrints
 from IPython.utils.path import compress_user
 from IPython.utils import py3compat
+from IPython.utils.signatures import Signature, Parameter
 
 
 #-----------------------------------------------------------------------------
@@ -49,7 +40,7 b' ip = get_ipython()'
 # defined, if any code is inserted above, the following line will need to be
 # updated.  Do NOT insert any whitespace between the next line and the function
 # definition below.
-THIS_LINE_NUMBER = 52  # Put here the actual number of this line
+THIS_LINE_NUMBER = 43  # Put here the actual number of this line
 def test_find_source_lines():
     nt.assert_equal(oinspect.find_source_lines(test_find_source_lines), 
                     THIS_LINE_NUMBER+1)
@@ -120,6 +111,14 b' class Call(object):'
     def method(self, x, z=2):
         """Some method's docstring"""
 
+class HasSignature(object):
+    """This is the class docstring."""
+    __signature__ = Signature([Parameter('test', Parameter.POSITIONAL_OR_KEYWORD)])
+
+    def __init__(self, *args):
+        """This is the init docstring"""
+
+
 class SimpleClass(object):
     def method(self, x, z=2):
         """Some method's docstring"""
@@ -282,7 +281,7 b' def test_info():'
     nt.assert_equal(i['docstring'], Call.__doc__)
     nt.assert_equal(i['source'], None)
     nt.assert_true(i['isclass'])
-    nt.assert_equal(i['init_definition'], "Call(self, x, y=1)\n")
+    nt.assert_equal(i['init_definition'], "Call(x, y=1)\n")
     nt.assert_equal(i['init_docstring'], Call.__init__.__doc__)
 
     i = inspector.info(Call, detail_level=1)
@@ -307,6 +306,11 b' def test_info():'
         nt.assert_equal(i['type_name'], 'instance')
         nt.assert_equal(i['docstring'], OldStyle.__doc__)
 
+def test_class_signature():
+    info = inspector.info(HasSignature, 'HasSignature')
+    nt.assert_equal(info['init_definition'], "HasSignature(test)\n")
+    nt.assert_equal(info['init_docstring'], HasSignature.__init__.__doc__)
+
 def test_info_awkward():
     # Just test that this doesn't throw an error.
     i = inspector.info(Awkward())