bpo-40636: PEP 618: add strict parameter to zip() (GH-20921)
zip() now supports PEP 618's strict parameter, which raises a
ValueError if the arguments are exhausted at different lengths.
Patch by Brandt Bucher.
Co-authored-by: Brandt Bucher <brandtbucher@gmail.com>
Co-authored-by: Ram Rachum <ram@rachum.com>
diff --git a/Lib/test/test_builtin.py b/Lib/test/test_builtin.py
index 290ba2c..40df7b6 100644
--- a/Lib/test/test_builtin.py
+++ b/Lib/test/test_builtin.py
@@ -1521,6 +1521,14 @@
self.assertRaises(TypeError, vars, 42)
self.assertEqual(vars(self.C_get_vars()), {'a':2})
+ def iter_error(self, iterable, error):
+ """Collect `iterable` into a list, catching an expected `error`."""
+ items = []
+ with self.assertRaises(error):
+ for item in iterable:
+ items.append(item)
+ return items
+
def test_zip(self):
a = (1, 2, 3)
b = (4, 5, 6)
@@ -1573,6 +1581,66 @@
z1 = zip(a, b)
self.check_iter_pickle(z1, t, proto)
+ def test_zip_pickle_strict(self):
+ a = (1, 2, 3)
+ b = (4, 5, 6)
+ t = [(1, 4), (2, 5), (3, 6)]
+ for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+ z1 = zip(a, b, strict=True)
+ self.check_iter_pickle(z1, t, proto)
+
+ def test_zip_pickle_strict_fail(self):
+ a = (1, 2, 3)
+ b = (4, 5, 6, 7)
+ t = [(1, 4), (2, 5), (3, 6)]
+ for proto in range(pickle.HIGHEST_PROTOCOL + 1):
+ z1 = zip(a, b, strict=True)
+ z2 = pickle.loads(pickle.dumps(z1, proto))
+ self.assertEqual(self.iter_error(z1, ValueError), t)
+ self.assertEqual(self.iter_error(z2, ValueError), t)
+
+ def test_zip_pickle_stability(self):
+ # Pickles of zip((1, 2, 3), (4, 5, 6)) dumped from 3.9:
+ pickles = [
+ b'citertools\nizip\np0\n(c__builtin__\niter\np1\n((I1\nI2\nI3\ntp2\ntp3\nRp4\nI0\nbg1\n((I4\nI5\nI6\ntp5\ntp6\nRp7\nI0\nbtp8\nRp9\n.',
+ b'citertools\nizip\nq\x00(c__builtin__\niter\nq\x01((K\x01K\x02K\x03tq\x02tq\x03Rq\x04K\x00bh\x01((K\x04K\x05K\x06tq\x05tq\x06Rq\x07K\x00btq\x08Rq\t.',
+ b'\x80\x02citertools\nizip\nq\x00c__builtin__\niter\nq\x01K\x01K\x02K\x03\x87q\x02\x85q\x03Rq\x04K\x00bh\x01K\x04K\x05K\x06\x87q\x05\x85q\x06Rq\x07K\x00b\x86q\x08Rq\t.',
+ b'\x80\x03cbuiltins\nzip\nq\x00cbuiltins\niter\nq\x01K\x01K\x02K\x03\x87q\x02\x85q\x03Rq\x04K\x00bh\x01K\x04K\x05K\x06\x87q\x05\x85q\x06Rq\x07K\x00b\x86q\x08Rq\t.',
+ b'\x80\x04\x95L\x00\x00\x00\x00\x00\x00\x00\x8c\x08builtins\x94\x8c\x03zip\x94\x93\x94\x8c\x08builtins\x94\x8c\x04iter\x94\x93\x94K\x01K\x02K\x03\x87\x94\x85\x94R\x94K\x00bh\x05K\x04K\x05K\x06\x87\x94\x85\x94R\x94K\x00b\x86\x94R\x94.',
+ b'\x80\x05\x95L\x00\x00\x00\x00\x00\x00\x00\x8c\x08builtins\x94\x8c\x03zip\x94\x93\x94\x8c\x08builtins\x94\x8c\x04iter\x94\x93\x94K\x01K\x02K\x03\x87\x94\x85\x94R\x94K\x00bh\x05K\x04K\x05K\x06\x87\x94\x85\x94R\x94K\x00b\x86\x94R\x94.',
+ ]
+ for protocol, dump in enumerate(pickles):
+ z1 = zip((1, 2, 3), (4, 5, 6))
+ z2 = zip((1, 2, 3), (4, 5, 6), strict=False)
+ z3 = pickle.loads(dump)
+ l3 = list(z3)
+ self.assertEqual(type(z3), zip)
+ self.assertEqual(pickle.dumps(z1, protocol), dump)
+ self.assertEqual(pickle.dumps(z2, protocol), dump)
+ self.assertEqual(list(z1), l3)
+ self.assertEqual(list(z2), l3)
+
+ def test_zip_pickle_strict_stability(self):
+ # Pickles of zip((1, 2, 3), (4, 5), strict=True) dumped from 3.10:
+ pickles = [
+ b'citertools\nizip\np0\n(c__builtin__\niter\np1\n((I1\nI2\nI3\ntp2\ntp3\nRp4\nI0\nbg1\n((I4\nI5\ntp5\ntp6\nRp7\nI0\nbtp8\nRp9\nI01\nb.',
+ b'citertools\nizip\nq\x00(c__builtin__\niter\nq\x01((K\x01K\x02K\x03tq\x02tq\x03Rq\x04K\x00bh\x01((K\x04K\x05tq\x05tq\x06Rq\x07K\x00btq\x08Rq\tI01\nb.',
+ b'\x80\x02citertools\nizip\nq\x00c__builtin__\niter\nq\x01K\x01K\x02K\x03\x87q\x02\x85q\x03Rq\x04K\x00bh\x01K\x04K\x05\x86q\x05\x85q\x06Rq\x07K\x00b\x86q\x08Rq\t\x88b.',
+ b'\x80\x03cbuiltins\nzip\nq\x00cbuiltins\niter\nq\x01K\x01K\x02K\x03\x87q\x02\x85q\x03Rq\x04K\x00bh\x01K\x04K\x05\x86q\x05\x85q\x06Rq\x07K\x00b\x86q\x08Rq\t\x88b.',
+ b'\x80\x04\x95L\x00\x00\x00\x00\x00\x00\x00\x8c\x08builtins\x94\x8c\x03zip\x94\x93\x94\x8c\x08builtins\x94\x8c\x04iter\x94\x93\x94K\x01K\x02K\x03\x87\x94\x85\x94R\x94K\x00bh\x05K\x04K\x05\x86\x94\x85\x94R\x94K\x00b\x86\x94R\x94\x88b.',
+ b'\x80\x05\x95L\x00\x00\x00\x00\x00\x00\x00\x8c\x08builtins\x94\x8c\x03zip\x94\x93\x94\x8c\x08builtins\x94\x8c\x04iter\x94\x93\x94K\x01K\x02K\x03\x87\x94\x85\x94R\x94K\x00bh\x05K\x04K\x05\x86\x94\x85\x94R\x94K\x00b\x86\x94R\x94\x88b.',
+ ]
+ a = (1, 2, 3)
+ b = (4, 5)
+ t = [(1, 4), (2, 5)]
+ for protocol, dump in enumerate(pickles):
+ z1 = zip(a, b, strict=True)
+ z2 = pickle.loads(dump)
+ self.assertEqual(pickle.dumps(z1, protocol), dump)
+ self.assertEqual(type(z2), zip)
+ self.assertEqual(self.iter_error(z1, ValueError), t)
+ self.assertEqual(self.iter_error(z2, ValueError), t)
+
def test_zip_bad_iterable(self):
exception = TypeError()
@@ -1585,6 +1653,88 @@
self.assertIs(cm.exception, exception)
+ def test_zip_strict(self):
+ self.assertEqual(tuple(zip((1, 2, 3), 'abc', strict=True)),
+ ((1, 'a'), (2, 'b'), (3, 'c')))
+ self.assertRaises(ValueError, tuple,
+ zip((1, 2, 3, 4), 'abc', strict=True))
+ self.assertRaises(ValueError, tuple,
+ zip((1, 2), 'abc', strict=True))
+ self.assertRaises(ValueError, tuple,
+ zip((1, 2), (1, 2), 'abc', strict=True))
+
+ def test_zip_strict_iterators(self):
+ x = iter(range(5))
+ y = [0]
+ z = iter(range(5))
+ self.assertRaises(ValueError, list,
+ (zip(x, y, z, strict=True)))
+ self.assertEqual(next(x), 2)
+ self.assertEqual(next(z), 1)
+
+ def test_zip_strict_error_handling(self):
+
+ class Error(Exception):
+ pass
+
+ class Iter:
+ def __init__(self, size):
+ self.size = size
+ def __iter__(self):
+ return self
+ def __next__(self):
+ self.size -= 1
+ if self.size < 0:
+ raise Error
+ return self.size
+
+ l1 = self.iter_error(zip("AB", Iter(1), strict=True), Error)
+ self.assertEqual(l1, [("A", 0)])
+ l2 = self.iter_error(zip("AB", Iter(2), "A", strict=True), ValueError)
+ self.assertEqual(l2, [("A", 1, "A")])
+ l3 = self.iter_error(zip("AB", Iter(2), "ABC", strict=True), Error)
+ self.assertEqual(l3, [("A", 1, "A"), ("B", 0, "B")])
+ l4 = self.iter_error(zip("AB", Iter(3), strict=True), ValueError)
+ self.assertEqual(l4, [("A", 2), ("B", 1)])
+ l5 = self.iter_error(zip(Iter(1), "AB", strict=True), Error)
+ self.assertEqual(l5, [(0, "A")])
+ l6 = self.iter_error(zip(Iter(2), "A", strict=True), ValueError)
+ self.assertEqual(l6, [(1, "A")])
+ l7 = self.iter_error(zip(Iter(2), "ABC", strict=True), Error)
+ self.assertEqual(l7, [(1, "A"), (0, "B")])
+ l8 = self.iter_error(zip(Iter(3), "AB", strict=True), ValueError)
+ self.assertEqual(l8, [(2, "A"), (1, "B")])
+
+ def test_zip_strict_error_handling_stopiteration(self):
+
+ class Iter:
+ def __init__(self, size):
+ self.size = size
+ def __iter__(self):
+ return self
+ def __next__(self):
+ self.size -= 1
+ if self.size < 0:
+ raise StopIteration
+ return self.size
+
+ l1 = self.iter_error(zip("AB", Iter(1), strict=True), ValueError)
+ self.assertEqual(l1, [("A", 0)])
+ l2 = self.iter_error(zip("AB", Iter(2), "A", strict=True), ValueError)
+ self.assertEqual(l2, [("A", 1, "A")])
+ l3 = self.iter_error(zip("AB", Iter(2), "ABC", strict=True), ValueError)
+ self.assertEqual(l3, [("A", 1, "A"), ("B", 0, "B")])
+ l4 = self.iter_error(zip("AB", Iter(3), strict=True), ValueError)
+ self.assertEqual(l4, [("A", 2), ("B", 1)])
+ l5 = self.iter_error(zip(Iter(1), "AB", strict=True), ValueError)
+ self.assertEqual(l5, [(0, "A")])
+ l6 = self.iter_error(zip(Iter(2), "A", strict=True), ValueError)
+ self.assertEqual(l6, [(1, "A")])
+ l7 = self.iter_error(zip(Iter(2), "ABC", strict=True), ValueError)
+ self.assertEqual(l7, [(1, "A"), (0, "B")])
+ l8 = self.iter_error(zip(Iter(3), "AB", strict=True), ValueError)
+ self.assertEqual(l8, [(2, "A"), (1, "B")])
+
def test_format(self):
# Test the basic machinery of the format() builtin. Don't test
# the specifics of the various formatters
diff --git a/Misc/NEWS.d/next/Core and Builtins/2020-06-17-10-27-17.bpo-40636.MYaCIe.rst b/Misc/NEWS.d/next/Core and Builtins/2020-06-17-10-27-17.bpo-40636.MYaCIe.rst
new file mode 100644
index 0000000..ba26ad9
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2020-06-17-10-27-17.bpo-40636.MYaCIe.rst
@@ -0,0 +1,3 @@
+:func:`zip` now supports :pep:`618`'s ``strict`` parameter, which raises a
+:exc:`ValueError` if the arguments are exhausted at different lengths.
+Patch by Brandt Bucher.
diff --git a/Python/bltinmodule.c b/Python/bltinmodule.c
index 65f9528..c6ede1c 100644
--- a/Python/bltinmodule.c
+++ b/Python/bltinmodule.c
@@ -2517,9 +2517,10 @@
typedef struct {
PyObject_HEAD
- Py_ssize_t tuplesize;
- PyObject *ittuple; /* tuple of iterators */
+ Py_ssize_t tuplesize;
+ PyObject *ittuple; /* tuple of iterators */
PyObject *result;
+ int strict;
} zipobject;
static PyObject *
@@ -2530,9 +2531,21 @@
PyObject *ittuple; /* tuple of iterators */
PyObject *result;
Py_ssize_t tuplesize;
+ int strict = 0;
- if (type == &PyZip_Type && !_PyArg_NoKeywords("zip", kwds))
- return NULL;
+ if (kwds) {
+ PyObject *empty = PyTuple_New(0);
+ if (empty == NULL) {
+ return NULL;
+ }
+ static char *kwlist[] = {"strict", NULL};
+ int parsed = PyArg_ParseTupleAndKeywords(
+ empty, kwds, "|$p:zip", kwlist, &strict);
+ Py_DECREF(empty);
+ if (!parsed) {
+ return NULL;
+ }
+ }
/* args must be a tuple */
assert(PyTuple_Check(args));
@@ -2573,6 +2586,7 @@
lz->ittuple = ittuple;
lz->tuplesize = tuplesize;
lz->result = result;
+ lz->strict = strict;
return (PyObject *)lz;
}
@@ -2613,6 +2627,9 @@
item = (*Py_TYPE(it)->tp_iternext)(it);
if (item == NULL) {
Py_DECREF(result);
+ if (lz->strict) {
+ goto check;
+ }
return NULL;
}
olditem = PyTuple_GET_ITEM(result, i);
@@ -2628,28 +2645,85 @@
item = (*Py_TYPE(it)->tp_iternext)(it);
if (item == NULL) {
Py_DECREF(result);
+ if (lz->strict) {
+ goto check;
+ }
return NULL;
}
PyTuple_SET_ITEM(result, i, item);
}
}
return result;
+check:
+ if (PyErr_Occurred()) {
+ if (!PyErr_ExceptionMatches(PyExc_StopIteration)) {
+ // next() on argument i raised an exception (not StopIteration)
+ return NULL;
+ }
+ PyErr_Clear();
+ }
+ if (i) {
+ // ValueError: zip() argument 2 is shorter than argument 1
+ // ValueError: zip() argument 3 is shorter than arguments 1-2
+ const char* plural = i == 1 ? " " : "s 1-";
+ return PyErr_Format(PyExc_ValueError,
+ "zip() argument %d is shorter than argument%s%d",
+ i + 1, plural, i);
+ }
+ for (i = 1; i < tuplesize; i++) {
+ it = PyTuple_GET_ITEM(lz->ittuple, i);
+ item = (*Py_TYPE(it)->tp_iternext)(it);
+ if (item) {
+ Py_DECREF(item);
+ const char* plural = i == 1 ? " " : "s 1-";
+ return PyErr_Format(PyExc_ValueError,
+ "zip() argument %d is longer than argument%s%d",
+ i + 1, plural, i);
+ }
+ if (PyErr_Occurred()) {
+ if (!PyErr_ExceptionMatches(PyExc_StopIteration)) {
+ // next() on argument i raised an exception (not StopIteration)
+ return NULL;
+ }
+ PyErr_Clear();
+ }
+ // Argument i is exhausted. So far so good...
+ }
+ // All arguments are exhausted. Success!
+ return NULL;
}
static PyObject *
zip_reduce(zipobject *lz, PyObject *Py_UNUSED(ignored))
{
/* Just recreate the zip with the internal iterator tuple */
- return Py_BuildValue("OO", Py_TYPE(lz), lz->ittuple);
+ if (lz->strict) {
+ return PyTuple_Pack(3, Py_TYPE(lz), lz->ittuple, Py_True);
+ }
+ return PyTuple_Pack(2, Py_TYPE(lz), lz->ittuple);
+}
+
+PyDoc_STRVAR(setstate_doc, "Set state information for unpickling.");
+
+static PyObject *
+zip_setstate(zipobject *lz, PyObject *state)
+{
+ int strict = PyObject_IsTrue(state);
+ if (strict < 0) {
+ return NULL;
+ }
+ lz->strict = strict;
+ Py_RETURN_NONE;
}
static PyMethodDef zip_methods[] = {
{"__reduce__", (PyCFunction)zip_reduce, METH_NOARGS, reduce_doc},
- {NULL, NULL} /* sentinel */
+ {"__setstate__", (PyCFunction)zip_setstate, METH_O, setstate_doc},
+ {NULL} /* sentinel */
};
PyDoc_STRVAR(zip_doc,
-"zip(*iterables) --> A zip object yielding tuples until an input is exhausted.\n\
+"zip(*iterables, strict=False) --> Yield tuples until an input is exhausted.\n\
\n\
>>> list(zip('abcdefg', range(3), range(4)))\n\
[('a', 0, 0), ('b', 1, 1), ('c', 2, 2)]\n\
@@ -2657,7 +2731,10 @@
The zip object yields n-length tuples, where n is the number of iterables\n\
passed as positional arguments to zip(). The i-th element in every tuple\n\
comes from the i-th iterable argument to zip(). This continues until the\n\
-shortest argument is exhausted.");
+shortest argument is exhausted.\n\
+\n\
+If strict is true and one of the arguments is exhausted before the others,\n\
+raise a ValueError.");
PyTypeObject PyZip_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)