Merged revisions 79674 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/trunk

........
  r79674 | mark.dickinson | 2010-04-03 15:05:10 +0100 (Sat, 03 Apr 2010) | 3 lines

  Issue #8300:  Let struct.pack use __index__ to convert and pack non-integers.
  Based on a patch by Meador Inge.
........

diff --git a/Doc/library/struct.rst b/Doc/library/struct.rst
index bee154f07ab2ab8fc67f6018d1d3b1ebe0d0678c..ee949d9f60701cba33b40ef695f08fab163a031f 100644 (file)
--- a/Doc/library/struct.rst
+++ b/Doc/library/struct.rst
@@ -119,6 +119,15 @@ Notes:
    the platform C compiler supports C :ctype:`long long`, or, on Windows,
    :ctype:`__int64`.  They are always available in standard modes.
 
+(4)
+   When attempting to pack a non-integer using any of the integer conversion
+   codes, if the non-integer has a :meth:`__index__` method then that method is
+   called to convert the argument to an integer before packing.
+
+   .. versionchanged:: 3.2
+      Use of the :meth:`__index__` method for non-integers is new in 3.2.
+
+
 A format character may be preceded by an integral repeat count.  For example,
 the format string ``'4h'`` means exactly the same as ``'hhhh'``.
 

diff --git a/Lib/test/test_struct.py b/Lib/test/test_struct.py
index 39ccb27017aaf454d85255d68937ec4076669baa..3d67abdb3dd3411780fb94de818c9e5d11787571 100644 (file)
--- a/Lib/test/test_struct.py
+++ b/Lib/test/test_struct.py
@@ -282,6 +282,23 @@ class StructTest(unittest.TestCase):
                                   struct.pack, self.format,
                                   NotAnInt)
 
+                # Objects with an '__index__' method should be allowed
+                # to pack as integers.
+                class Indexable(object):
+                    def __init__(self, value):
+                        self._value = value
+
+                    def __index__(self):
+                        return self._value
+
+                for obj in (Indexable(0), Indexable(10), Indexable(17),
+                            Indexable(42), Indexable(100), Indexable(127)):
+                    try:
+                        struct.pack(format, obj)
+                    except:
+                        self.fail("integer code pack failed on object "
+                                  "with '__index__' method")
+
         for code in integer_codes:
             for byteorder in byteorders:
                 if (byteorder in ('', '@') and code in ('q', 'Q') and

diff --git a/Misc/NEWS b/Misc/NEWS
index a1465d768022bc864e17f62eada2f039fcabb076..a15fa917546a75fa6ffd2b65ae8cfd84ccabf490 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -879,6 +879,11 @@ Library
 Extension Modules
 -----------------
 
+- Issue #8300: When passing a non-integer argument to struct.pack with any
+  integer format code, struct.pack first attempts to convert the non-integer
+  using its __index__ method.  If that method is non-existent or raises
+  TypeError it goes on to try the __int__ method, as described below.
+
 - Issue #8142: Update libffi to the 3.0.9 release.
 
 - Issue #6949: Allow the _dbm extension to be built with db 4.8.x.

diff --git a/Modules/_struct.c b/Modules/_struct.c
index 43321a4e3daa459dfd50e71bac9af8634d5438dc..e21487d05c691657b9e5707d04c7eeb609d59882 100644 (file)
--- a/Modules/_struct.c
+++ b/Modules/_struct.c
@@ -97,12 +97,27 @@ get_pylong(PyObject *v)
 {
        assert(v != NULL);
        if (!PyLong_Check(v)) {
-               PyErr_SetString(StructError,
-                               "required argument is not an integer");
-               return NULL;
+               /* Not an integer;  try to use __index__ to convert. */
+               if (PyIndex_Check(v)) {
+                       v = PyNumber_Index(v);
+                       if (v == NULL)
+                               return NULL;
+                       if (!PyLong_Check(v)) {
+                               PyErr_SetString(PyExc_TypeError,
+                                               "__index__ method "
+                                               "returned non-integer");
+                               return NULL;
+                       }
+               }
+               else {
+                       PyErr_SetString(StructError,
+                                       "required argument is not an integer");
+                       return NULL;
+               }
        }
+       else
+               Py_INCREF(v);
 
-       Py_INCREF(v);
        return v;
 }