New submission from Ryan Freckleton:
This is a patch to implement a product() builtin function. It works
behaves similarly to reduce(operator.mul,...) but is implemented in C.
Tests and documentation are included in this patch.
----------
components: Documentation, Library (Lib), Tests
files: product_function.diff
messages: 55599
nosy: ryan.freckleton
severity: normal
status: open
title: product function patch
type: behavior
versions: Python 2.6
__________________________________
Tracker <[EMAIL PROTECTED]>
<http://bugs.python.org/issue1093>
__________________________________
Index: Python/bltinmodule.c
===================================================================
--- Python/bltinmodule.c (revision 57913)
+++ Python/bltinmodule.c (working copy)
@@ -2094,7 +2094,59 @@
of parameter 'start' (which defaults to 0). When the sequence is\n\
empty, returns start.");
+static PyObject*
+builtin_product(PyObject *self, PyObject *args)
+{
+ PyObject *seq;
+ PyObject *result = NULL;
+ PyObject *temp, *item, *iter;
+ if (!PyArg_UnpackTuple(args, "product", 1, 2, &seq, &result))
+ return NULL;
+
+ iter = PyObject_GetIter(seq);
+ if (iter == NULL)
+ return NULL;
+
+ if (result == NULL) {
+ result = PyInt_FromLong(1);
+ if (result == NULL) {
+ Py_DECREF(iter);
+ return NULL;
+ }
+ } else {
+ Py_INCREF(result);
+ }
+
+ for(;;) {
+ item = PyIter_Next(iter);
+ if (item == NULL) {
+ /* error, or end-of-sequence */
+ if (PyErr_Occurred()) {
+ Py_DECREF(result);
+ result = NULL;
+ }
+ break;
+ }
+ temp = PyNumber_Multiply(result, item);
+ Py_DECREF(result);
+ Py_DECREF(item);
+ result = temp;
+ if (result == NULL)
+ break;
+ }
+ Py_DECREF(iter);
+ return result;
+}
+
+PyDoc_STRVAR(product_doc,
+"product(sequence[, start]) -> value\n\
+\n\
+Returns the product of a sequence of numbers times the value\n\
+of parameter 'start' (which defaults to 1). When the sequence is\n\
+empty, returns start.");
+
+
static PyObject *
builtin_isinstance(PyObject *self, PyObject *args)
{
@@ -2296,6 +2348,7 @@
{"open", (PyCFunction)builtin_open, METH_VARARGS | METH_KEYWORDS, open_doc},
{"ord", builtin_ord, METH_O, ord_doc},
{"pow", builtin_pow, METH_VARARGS, pow_doc},
+ {"product", builtin_product, METH_VARARGS, product_doc},
{"range", builtin_range, METH_VARARGS, range_doc},
{"raw_input", builtin_raw_input, METH_VARARGS, raw_input_doc},
{"reduce", builtin_reduce, METH_VARARGS, reduce_doc},
Index: Doc/library/functions.rst
===================================================================
--- Doc/library/functions.rst (revision 57913)
+++ Doc/library/functions.rst (working copy)
@@ -1104,7 +1104,15 @@
.. versionadded:: 2.3
+.. function:: product(iterable[, start])
+ Multiplies *start* and the items of an *iterable* from left to right and
+ returns the product. *start* defaults to ``1``. The *iterable*'s items are
+ normally numbers. Note that ``product(range(n), m)`` is equivalent to
+ ``reduce(operator.mul, range(n), m)``
+ .. versionadded:: 2.6
+
+
.. function:: super(type[, object-or-type])
Return the superclass of *type*. If the second argument is omitted the super
Index: Lib/test/test_builtin.py
===================================================================
--- Lib/test/test_builtin.py (revision 57913)
+++ Lib/test/test_builtin.py (working copy)
@@ -1697,6 +1697,19 @@
raise ValueError
self.assertRaises(ValueError, sum, BadSeq())
+ def test_product(self):
+ self.assertEqual(product([]), 1)
+ self.assertEqual(product(range(2,8)), 5040)
+ self.assertEqual(product(iter(range(2,8))), 5040)
+
+ self.assertRaises(TypeError, product)
+ self.assertRaises(TypeError, product, 42)
+ self.assertRaises(TypeError, product, ['a', 'b', 'c'])
+ self.assertRaises(TypeError, product, ['a', 'b', 'c'], '')
+ self.assertRaises(TypeError, product, [[1], [2], [3]])
+ self.assertRaises(TypeError, product, [{2:3}])
+ self.assertRaises(TypeError, product, [{2:3}]*2, {2:3})
+
def test_tuple(self):
self.assertEqual(tuple(()), ())
t0_3 = (0, 1, 2, 3)
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