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Revert "bpo-34410: Raise a RuntimeError when tee iterator is consumed from different threads." #15736

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Merged
merged 1 commit into from
Sep 9, 2019
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Revert "bpo-34410: Raise a RuntimeError when tee iterator is consumed from different threads." #15736

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3 changes: 1 addition & 2 deletions Doc/library/itertools.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -643,8 +643,7 @@ loops that truncate the stream.

Once :func:`tee` has made a split, the original *iterable* should not be
used anywhere else; otherwise, the *iterable* could get advanced without
the tee objects being informed. the :func:`tee` iterator can not be consumed
from different threads, even if an underlying iterator is thread-safe.
the tee objects being informed.

This itertool may require significant auxiliary storage (depending on how
much temporary data needs to be stored). In general, if one iterator uses
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2 changes: 0 additions & 2 deletions Misc/NEWS.d/next/Library/2019-08-29-10-26-57.bpo-34410.ttCIpm.rst
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8 changes: 0 additions & 8 deletions Modules/itertoolsmodule.c
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Expand Up @@ -452,7 +452,6 @@ typedef struct {
teedataobject *dataobj;
int index; /* 0 <= index <= LINKCELLS */
PyObject *weakreflist;
unsigned long thread_id;
} teeobject;

static PyTypeObject teedataobject_type;
Expand Down Expand Up @@ -681,11 +680,6 @@ tee_next(teeobject *to)
{
PyObject *value, *link;

if (to->thread_id != PyThread_get_thread_ident()) {
PyErr_SetString(PyExc_RuntimeError,
"tee() iterator can not be consumed from different threads.");
return NULL;
}
if (to->index >= LINKCELLS) {
link = teedataobject_jumplink(to->dataobj);
if (link == NULL)
Expand Down Expand Up @@ -719,7 +713,6 @@ tee_copy(teeobject *to, PyObject *Py_UNUSED(ignored))
newto->dataobj = to->dataobj;
newto->index = to->index;
newto->weakreflist = NULL;
newto->thread_id = to->thread_id;
PyObject_GC_Track(newto);
return (PyObject *)newto;
}
Expand Down Expand Up @@ -752,7 +745,6 @@ tee_fromiterable(PyObject *iterable)

to->index = 0;
to->weakreflist = NULL;
to->thread_id = PyThread_get_thread_ident();
PyObject_GC_Track(to);
done:
Py_XDECREF(it);
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