add introspection to range objects (closes #9896)
Patch by Daniel Urban.
diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index f9af3d8..3cf5335 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -1042,7 +1042,9 @@
...]``. If *step* is positive, the last element is the largest ``start + i *
step`` less than *stop*; if *step* is negative, the last element is the
smallest ``start + i * step`` greater than *stop*. *step* must not be zero
- (or else :exc:`ValueError` is raised). Example:
+ (or else :exc:`ValueError` is raised). Range objects have read-only data
+ attributes :attr:`start`, :attr:`stop` and :attr:`step` which return the
+ argument values (or their default). Example:
>>> list(range(10))
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
@@ -1100,6 +1102,9 @@
sequence of values they define (instead of comparing based on
object identity).
+ .. versionadded:: 3.3
+ The :attr:`start`, :attr:`stop` and :attr:`step` attributes.
+
.. function:: repr(object)
diff --git a/Lib/test/test_range.py b/Lib/test/test_range.py
index 6035e76..2e335cc 100644
--- a/Lib/test/test_range.py
+++ b/Lib/test/test_range.py
@@ -560,6 +560,35 @@
range(0) >= range(0)
+ def test_attributes(self):
+ # test the start, stop and step attributes of range objects
+ self.assert_attrs(range(0), 0, 0, 1)
+ self.assert_attrs(range(10), 0, 10, 1)
+ self.assert_attrs(range(-10), 0, -10, 1)
+ self.assert_attrs(range(0, 10, 1), 0, 10, 1)
+ self.assert_attrs(range(0, 10, 3), 0, 10, 3)
+ self.assert_attrs(range(10, 0, -1), 10, 0, -1)
+ self.assert_attrs(range(10, 0, -3), 10, 0, -3)
+
+ def assert_attrs(self, rangeobj, start, stop, step):
+ self.assertEqual(rangeobj.start, start)
+ self.assertEqual(rangeobj.stop, stop)
+ self.assertEqual(rangeobj.step, step)
+
+ with self.assertRaises(AttributeError):
+ rangeobj.start = 0
+ with self.assertRaises(AttributeError):
+ rangeobj.stop = 10
+ with self.assertRaises(AttributeError):
+ rangeobj.step = 1
+
+ with self.assertRaises(AttributeError):
+ del rangeobj.start
+ with self.assertRaises(AttributeError):
+ del rangeobj.stop
+ with self.assertRaises(AttributeError):
+ del rangeobj.step
+
def test_main():
test.support.run_unittest(RangeTest)
diff --git a/Objects/rangeobject.c b/Objects/rangeobject.c
index c1e9e54..fb6a5fe 100644
--- a/Objects/rangeobject.c
+++ b/Objects/rangeobject.c
@@ -1,6 +1,7 @@
/* Range object implementation */
#include "Python.h"
+#include "structmember.h"
/* Support objects whose length is > PY_SSIZE_T_MAX.
@@ -880,6 +881,13 @@
{NULL, NULL} /* sentinel */
};
+static PyMemberDef range_members[] = {
+ {"start", T_OBJECT_EX, offsetof(rangeobject, start), READONLY},
+ {"stop", T_OBJECT_EX, offsetof(rangeobject, stop), READONLY},
+ {"step", T_OBJECT_EX, offsetof(rangeobject, step), READONLY},
+ {0}
+};
+
PyTypeObject PyRange_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"range", /* Name of this type */
@@ -909,7 +917,7 @@
range_iter, /* tp_iter */
0, /* tp_iternext */
range_methods, /* tp_methods */
- 0, /* tp_members */
+ range_members, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */