gh-72793: C implementation of parts of copy.deepcopy

Include/internal/pycore_dict.h

@@ -44,6 +44,8 @@ extern int _PyDict_HasOnlyStringKeys(PyObject *mp);
 
 extern void _PyDict_MaybeUntrack(PyObject *mp);
 
+// Export for '_copy' shared extension
+PyAPI_FUNC(PyObject*) _PyDict_NewPresized(Py_ssize_t minused);
 // Export for '_ctypes' shared extension
 PyAPI_FUNC(Py_ssize_t) _PyDict_SizeOf(PyDictObject *);
 

Lib/copy.py

@@ -116,9 +116,11 @@ def _copy_immutable(x):
 
 del d, t
 
-def deepcopy(x, memo=None, _nil=[]):
+def _deepcopy_fallback(x, memo=None, _nil=[]):
  """Deep copy operation on arbitrary Python objects.
 
+ This is the fallback from the C accelerator, and the main implementation if the C accelerator is not available.
+
  See the module's __doc__ string for more info.
  """
 
@@ -171,6 +173,13 @@ def deepcopy(x, memo=None, _nil=[]):
  _keep_alive(x, memo) # Make sure x lives at least as long as d
  return y
 
+try:
+ from _copy import deepcopy
+except ImportError:
+ # the fallback is for projects like PyPy that reuse the stdlib
+ deepcopy = _deepcopy_fallback
+ deepcopy.__name__ = 'deepcopy'
+
 _atomic_types ={types.NoneType, types.EllipsisType, types.NotImplementedType,
  int, float, bool, complex, bytes, str, types.CodeType, type, range,
  types.BuiltinFunctionType, types.FunctionType, weakref.ref, property}

Lib/test/test_capi/test_misc.py

@@ -294,7 +294,7 @@ def test_getitem_with_error(self):
  r'Current thread .* \(most recent call first\):\n'
  r' File .*, line 6 in <module>\n'
  r'\n'
- r'Extension modules: _testcapi \(total: 1\)\n')
+ r'Extension modules: .* \(total: 1\)\n')
  else:
  # Python built with NDEBUG macro defined:
  # test _Py_CheckFunctionResult() instead.