bpo-28598: Support __rmod__ for RHS subclasses of str in % string formatting operations (GH-366)
diff --git a/Lib/test/test_str.py b/Lib/test/test_str.py
index 5bb9f48..8b306f4 100644
--- a/Lib/test/test_str.py
+++ b/Lib/test/test_str.py
@@ -465,6 +465,15 @@
self.assertIn('str', exc)
self.assertIn('tuple', exc)
+ def test_issue28598_strsubclass_rhs(self):
+ # A subclass of str with an __rmod__ method should be able to hook
+ # into the % operator
+ class SubclassedStr(str):
+ def __rmod__(self, other):
+ return 'Success, self.__rmod__({!r}) was called'.format(other)
+ self.assertEqual('lhs %% %r' % SubclassedStr('rhs'),
+ "Success, self.__rmod__('lhs %% %r') was called")
+
def test_main():
test_support.run_unittest(StrTest)
diff --git a/Misc/NEWS b/Misc/NEWS
index 4523df5..407bf0f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
Core and Builtins
-----------------
+- bpo-28598: Support __rmod__ for subclasses of str being called before
+ str.__mod__. Patch by Martijn Pieters.
+
- bpo-29602: Fix incorrect handling of signed zeros in complex constructor for
complex subclasses and for inputs having a __complex__ method. Patch
by Serhiy Storchaka.
diff --git a/Python/ceval.c b/Python/ceval.c
index 2af78ff..733f077 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1446,10 +1446,14 @@
{
w = POP();
v = TOP();
- if (PyString_CheckExact(v))
+ if (PyString_CheckExact(v)
+ && (!PyString_Check(w) || PyString_CheckExact(w))) {
+ /* fast path; string formatting, but not if the RHS is a str subclass
+ (see issue28598) */
x = PyString_Format(v, w);
- else
+ } else {
x = PyNumber_Remainder(v, w);
+ }
Py_DECREF(v);
Py_DECREF(w);
SET_TOP(x);