mirror of https://github.com/python/cpython
gh-125916: Allow functools.reduce() 'initial' to be a keyword argument (#125917)
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@ -453,7 +453,7 @@ The :mod:`functools` module defines the following functions:
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.. versionadded:: 3.4
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.. function:: reduce(function, iterable[, initial], /)
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.. function:: reduce(function, iterable, /[, initial])
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Apply *function* of two arguments cumulatively to the items of *iterable*, from
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left to right, so as to reduce the iterable to a single value. For example,
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@ -468,7 +468,7 @@ The :mod:`functools` module defines the following functions:
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initial_missing = object()
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def reduce(function, iterable, initial=initial_missing, /):
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def reduce(function, iterable, /, initial=initial_missing):
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it = iter(iterable)
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if initial is initial_missing:
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value = next(it)
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@ -481,6 +481,9 @@ The :mod:`functools` module defines the following functions:
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See :func:`itertools.accumulate` for an iterator that yields all intermediate
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values.
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.. versionchanged:: next
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*initial* is now supported as a keyword argument.
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.. decorator:: singledispatch
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Transform a function into a :term:`single-dispatch <single
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@ -320,6 +320,11 @@ functools
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to reserve a place for positional arguments.
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(Contributed by Dominykas Grigonis in :gh:`119127`.)
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* Allow the *initial* parameter of :func:`functools.reduce` to be passed
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as a keyword argument.
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(Contributed by Sayandip Dutta in :gh:`125916`.)
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getopt
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------
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@ -236,7 +236,7 @@ _initial_missing = object()
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def reduce(function, sequence, initial=_initial_missing):
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"""
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reduce(function, iterable[, initial], /) -> value
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reduce(function, iterable, /[, initial]) -> value
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Apply a function of two arguments cumulatively to the items of an iterable, from left to right.
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@ -1005,6 +1005,29 @@ class TestReduce:
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d = {"one": 1, "two": 2, "three": 3}
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self.assertEqual(self.reduce(add, d), "".join(d.keys()))
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# test correctness of keyword usage of `initial` in `reduce`
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def test_initial_keyword(self):
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def add(x, y):
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return x + y
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self.assertEqual(
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self.reduce(add, ['a', 'b', 'c'], ''),
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self.reduce(add, ['a', 'b', 'c'], initial=''),
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)
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self.assertEqual(
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self.reduce(add, [['a', 'c'], [], ['d', 'w']], []),
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self.reduce(add, [['a', 'c'], [], ['d', 'w']], initial=[]),
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)
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self.assertEqual(
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self.reduce(lambda x, y: x*y, range(2,8), 1),
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self.reduce(lambda x, y: x*y, range(2,8), initial=1),
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)
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self.assertEqual(
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self.reduce(lambda x, y: x*y, range(2,21), 1),
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self.reduce(lambda x, y: x*y, range(2,21), initial=1),
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)
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self.assertRaises(TypeError, self.reduce, add, [0, 1], initial="")
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self.assertEqual(self.reduce(42, "", initial="1"), "1") # func is never called with one item
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@unittest.skipUnless(c_functools, 'requires the C _functools module')
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class TestReduceC(TestReduce, unittest.TestCase):
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@ -485,6 +485,7 @@ Luke Dunstan
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Virgil Dupras
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Bruno Dupuis
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Andy Dustman
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Sayandip Dutta
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Gary Duzan
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Eugene Dvurechenski
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Karmen Dykstra
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@ -0,0 +1,2 @@
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Allow the *initial* parameter of :func:`functools.reduce` to be passed as a keyword argument.
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Patch by Sayandip Dutta.
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@ -937,8 +937,8 @@ _functools.reduce
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function as func: object
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iterable as seq: object
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initial as result: object = NULL
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/
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initial as result: object = NULL
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Apply a function of two arguments cumulatively to the items of an iterable, from left to right.
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@ -953,7 +953,7 @@ calculates ((((1 + 2) + 3) + 4) + 5).
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static PyObject *
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_functools_reduce_impl(PyObject *module, PyObject *func, PyObject *seq,
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PyObject *result)
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/*[clinic end generated code: output=30d898fe1267c79d input=d233c2670cba7f66]*/
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/*[clinic end generated code: output=30d898fe1267c79d input=1511e9a8c38581ac]*/
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{
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PyObject *args, *it;
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@ -69,7 +69,7 @@ exit:
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}
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PyDoc_STRVAR(_functools_reduce__doc__,
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"reduce($module, function, iterable, initial=<unrepresentable>, /)\n"
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"reduce($module, function, iterable, /, initial=<unrepresentable>)\n"
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"--\n"
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"\n"
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"Apply a function of two arguments cumulatively to the items of an iterable, from left to right.\n"
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@ -82,30 +82,59 @@ PyDoc_STRVAR(_functools_reduce__doc__,
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"calculates ((((1 + 2) + 3) + 4) + 5).");
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#define _FUNCTOOLS_REDUCE_METHODDEF \
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{"reduce", _PyCFunction_CAST(_functools_reduce), METH_FASTCALL, _functools_reduce__doc__},
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{"reduce", _PyCFunction_CAST(_functools_reduce), METH_FASTCALL|METH_KEYWORDS, _functools_reduce__doc__},
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static PyObject *
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_functools_reduce_impl(PyObject *module, PyObject *func, PyObject *seq,
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PyObject *result);
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static PyObject *
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_functools_reduce(PyObject *module, PyObject *const *args, Py_ssize_t nargs)
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_functools_reduce(PyObject *module, PyObject *const *args, Py_ssize_t nargs, PyObject *kwnames)
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{
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PyObject *return_value = NULL;
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#if defined(Py_BUILD_CORE) && !defined(Py_BUILD_CORE_MODULE)
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#define NUM_KEYWORDS 1
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static struct {
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PyGC_Head _this_is_not_used;
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PyObject_VAR_HEAD
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PyObject *ob_item[NUM_KEYWORDS];
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} _kwtuple = {
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.ob_base = PyVarObject_HEAD_INIT(&PyTuple_Type, NUM_KEYWORDS)
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.ob_item = { &_Py_ID(initial), },
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};
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#undef NUM_KEYWORDS
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#define KWTUPLE (&_kwtuple.ob_base.ob_base)
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#else // !Py_BUILD_CORE
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# define KWTUPLE NULL
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#endif // !Py_BUILD_CORE
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static const char * const _keywords[] = {"", "", "initial", NULL};
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static _PyArg_Parser _parser = {
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.keywords = _keywords,
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.fname = "reduce",
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.kwtuple = KWTUPLE,
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};
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#undef KWTUPLE
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PyObject *argsbuf[3];
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Py_ssize_t noptargs = nargs + (kwnames ? PyTuple_GET_SIZE(kwnames) : 0) - 2;
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PyObject *func;
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PyObject *seq;
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PyObject *result = NULL;
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if (!_PyArg_CheckPositional("reduce", nargs, 2, 3)) {
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args = _PyArg_UnpackKeywords(args, nargs, NULL, kwnames, &_parser,
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/*minpos*/ 2, /*maxpos*/ 3, /*minkw*/ 0, /*varpos*/ 0, argsbuf);
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if (!args) {
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goto exit;
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}
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func = args[0];
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seq = args[1];
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if (nargs < 3) {
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goto skip_optional;
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if (!noptargs) {
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goto skip_optional_pos;
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}
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result = args[2];
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skip_optional:
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skip_optional_pos:
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return_value = _functools_reduce_impl(module, func, seq, result);
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exit:
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@ -159,4 +188,4 @@ _functools__lru_cache_wrapper_cache_clear(PyObject *self, PyObject *Py_UNUSED(ig
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return return_value;
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}
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/*[clinic end generated code: output=0c3df7e5131200b7 input=a9049054013a1b77]*/
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/*[clinic end generated code: output=e6edcc01f0720daf input=a9049054013a1b77]*/
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