[Python-checkins] bpo-32604: Add support for a "default" arg in channel_recv(). (GH-19770)
Eric Snow
webhook-mailer at python.org
Tue Apr 28 19:11:37 EDT 2020
https://github.com/python/cpython/commit/5e8c691594d68925213d36296ce7c4b3e90bcb1d
commit: 5e8c691594d68925213d36296ce7c4b3e90bcb1d
branch: master
author: Eric Snow <ericsnowcurrently at gmail.com>
committer: GitHub <noreply at github.com>
date: 2020-04-28T16:11:32-07:00
summary:
bpo-32604: Add support for a "default" arg in channel_recv(). (GH-19770)
This allows the caller to avoid creation of an exception when the channel is empty (just like `dict.get()` works). `ChannelEmptyError` is still raised if no default is provided.
Automerge-Triggered-By: @ericsnowcurrently
files:
M Lib/test/test__xxsubinterpreters.py
M Modules/_xxsubinterpretersmodule.c
diff --git a/Lib/test/test__xxsubinterpreters.py b/Lib/test/test__xxsubinterpreters.py
index 30f8f98acc9dd..8a368dc113972 100644
--- a/Lib/test/test__xxsubinterpreters.py
+++ b/Lib/test/test__xxsubinterpreters.py
@@ -1302,6 +1302,27 @@ def test_recv_empty(self):
with self.assertRaises(interpreters.ChannelEmptyError):
interpreters.channel_recv(cid)
+ def test_recv_default(self):
+ default = object()
+ cid = interpreters.channel_create()
+ obj1 = interpreters.channel_recv(cid, default)
+ interpreters.channel_send(cid, None)
+ interpreters.channel_send(cid, 1)
+ interpreters.channel_send(cid, b'spam')
+ interpreters.channel_send(cid, b'eggs')
+ obj2 = interpreters.channel_recv(cid, default)
+ obj3 = interpreters.channel_recv(cid, default)
+ obj4 = interpreters.channel_recv(cid)
+ obj5 = interpreters.channel_recv(cid, default)
+ obj6 = interpreters.channel_recv(cid, default)
+
+ self.assertIs(obj1, default)
+ self.assertIs(obj2, None)
+ self.assertEqual(obj3, 1)
+ self.assertEqual(obj4, b'spam')
+ self.assertEqual(obj5, b'eggs')
+ self.assertIs(obj6, default)
+
def test_run_string_arg_unresolved(self):
cid = interpreters.channel_create()
interp = interpreters.create()
diff --git a/Modules/_xxsubinterpretersmodule.c b/Modules/_xxsubinterpretersmodule.c
index fa35e14c55401..2ee8d07d0671f 100644
--- a/Modules/_xxsubinterpretersmodule.c
+++ b/Modules/_xxsubinterpretersmodule.c
@@ -1350,19 +1350,16 @@ _channel_recv(_channels *channels, int64_t id)
_PyCrossInterpreterData *data = _channel_next(chan, PyInterpreterState_GetID(interp));
PyThread_release_lock(mutex);
if (data == NULL) {
- if (!PyErr_Occurred()) {
- PyErr_Format(ChannelEmptyError, "channel %" PRId64 " is empty", id);
- }
return NULL;
}
// Convert the data back to an object.
PyObject *obj = _PyCrossInterpreterData_NewObject(data);
+ _PyCrossInterpreterData_Release(data);
+ PyMem_Free(data);
if (obj == NULL) {
return NULL;
}
- _PyCrossInterpreterData_Release(data);
- PyMem_Free(data);
return obj;
}
@@ -2351,20 +2348,37 @@ Add the object's data to the channel's queue.");
static PyObject *
channel_recv(PyObject *self, PyObject *args, PyObject *kwds)
{
- static char *kwlist[] = {"cid", NULL};
+ static char *kwlist[] = {"cid", "default", NULL};
int64_t cid;
- if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&:channel_recv", kwlist,
- channel_id_converter, &cid)) {
+ PyObject *dflt = NULL;
+ if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&|O:channel_recv", kwlist,
+ channel_id_converter, &cid, &dflt)) {
return NULL;
}
+ Py_XINCREF(dflt);
- return _channel_recv(&_globals.channels, cid);
+ PyObject *obj = _channel_recv(&_globals.channels, cid);
+ if (obj != NULL) {
+ Py_XDECREF(dflt);
+ return obj;
+ } else if (PyErr_Occurred()) {
+ Py_XDECREF(dflt);
+ return NULL;
+ } else if (dflt != NULL) {
+ return dflt;
+ } else {
+ PyErr_Format(ChannelEmptyError, "channel %" PRId64 " is empty", cid);
+ return NULL;
+ }
}
PyDoc_STRVAR(channel_recv_doc,
-"channel_recv(cid) -> obj\n\
+"channel_recv(cid, [default]) -> obj\n\
+\n\
+Return a new object from the data at the front of the channel's queue.\n\
\n\
-Return a new object from the data at the from of the channel's queue.");
+If there is nothing to receive then raise ChannelEmptyError, unless\n\
+a default value is provided. In that case return it.");
static PyObject *
channel_close(PyObject *self, PyObject *args, PyObject *kwds)
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