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‎Doc/c-api/exceptions.rst‎

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@@ -90,6 +90,16 @@ in various ways. There is a separate error indicator for each thread.
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the class in that case. If the values are already normalized, nothing happens.
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The delayed normalization is implemented to improve performance.
9292
93+
.. note::
94+
95+
This function *does not* implicitly set the ``__traceback__``
96+
attribute on the exception value. If setting the traceback
97+
appropriately is desired, the following additional snippet is needed::
98+
99+
if (tb != NULL) {
100+
PyException_SetTraceback(val, tb);
101+
}
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.. c:function:: void PyErr_Clear()
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‎Doc/library/concurrent.futures.rst‎

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@@ -371,7 +371,8 @@ Module Functions
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372372
Returns an iterator over the :class:`Future` instances (possibly created by
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different :class:`Executor` instances) given by *fs* that yields futures as
374-
they complete (finished or were cancelled). Any futures that completed
374+
they complete (finished or were cancelled). Any futures given by *fs* that
375+
are duplicated will be returned once. Any futures that completed
375376
before :func:`as_completed` is called will be yielded first. The returned
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iterator raises a :exc:`TimeoutError` if :meth:`~iterator.__next__` is
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called and the result isn't available after *timeout* seconds from the

‎Doc/reference/expressions.rst‎

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@@ -319,27 +319,25 @@ Yield expressions
319319
yield_atom: "(" `yield_expression` ")"
320320
yield_expression: "yield" [`expression_list` | "from" `expression`]
321321

322-
The :keyword:`yield` expression is only used when defining a :term:`generator`
323-
function,
324-
and can only be used in the body of a function definition. Using a
325-
:keyword:`yield` expression in a function definition is sufficient to cause that
326-
definition to create a generator function instead of a normal function.
322+
The yield expression is only used when defining a :term:`generator` function and
323+
thus can only be used in the body of a function definition. Using a yield
324+
expression in a function's body causes that function to be a generator.
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328326
When a generator function is called, it returns an iterator known as a
329327
generator. That generator then controls the execution of a generator function.
330328
The execution starts when one of the generator's methods is called. At that
331-
time, the execution proceeds to the first :keyword:`yield` expression, where it
332-
is suspended again, returning the value of :token:`expression_list` to
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generator's caller. By suspended we mean that all local state is retained,
334-
including the current bindings of local variables, the instruction pointer, and
335-
the internal evaluation stack. When the execution is resumed by calling one of
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the generator's methods, the function can proceed exactly as if the
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:keyword:`yield` expression was just another external call. The value of the
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:keyword:`yield` expression after resuming depends on the method which resumed
339-
the execution. If :meth:`~generator.__next__` is used (typically via either a
340-
:keyword:`for` or the :func:`next` builtin) then the result is :const:`None`,
341-
otherwise, if :meth:`~generator.send` is used, then the result will be the
342-
value passed in to that method.
329+
time, the execution proceeds to the first yield expression, where it is
330+
suspended again, returning the value of :token:`expression_list` to generator's
331+
caller. By suspended, we mean that all local state is retained, including the
332+
current bindings of local variables, the instruction pointer, and the internal
333+
evaluation stack. When the execution is resumed by calling one of the
334+
generator's methods, the function can proceed exactly as if the yield expression
335+
was just another external call. The value of the yield expression after
336+
resuming depends on the method which resumed the execution. If
337+
:meth:`~generator.__next__` is used (typically via either a :keyword:`for` or
338+
the :func:`next` builtin) then the result is :const:`None`. Otherwise, if
339+
:meth:`~generator.send` is used, then the result will be the value passed in to
340+
that method.
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344342
.. index:: single: coroutine
345343

@@ -349,11 +347,11 @@ suspended. The only difference is that a generator function cannot control
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where should the execution continue after it yields; the control is always
350348
transferred to the generator's caller.
351349

352-
:keyword:`yield` expressions are allowed in the :keyword:`try` clause of a
353-
:keyword:`try` ... :keyword:`finally` construct. If the generator is not
354-
resumed before it is finalized (by reaching a zero reference count or by being
355-
garbage collected), the generator-iterator's :meth:`~generator.close` method
356-
will be called, allowing any pending :keyword:`finally` clauses to execute.
350+
yield expressions are allowed in the :keyword:`try` clause of a :keyword:`try`
351+
... :keyword:`finally` construct. If the generator is not resumed before it is
352+
finalized (by reaching a zero reference count or by being garbage collected),
353+
the generator-iterator's :meth:`~generator.close` method will be called,
354+
allowing any pending :keyword:`finally` clauses to execute.
357355

358356
When ``yield from <expr>`` is used, it treats the supplied expression as
359357
a subiterator. All values produced by that subiterator are passed directly
@@ -373,11 +371,23 @@ the yield expression. It can be either set explicitly when raising
373371
.. versionchanged:: 3.3
374372
Added ``yield from <expr>`` to delegate control flow to a subiterator
375373

376-
The parentheses can be omitted when the :keyword:`yield` expression is the
377-
sole expression on the right hand side of an assignment statement.
374+
The parentheses may be omitted when the yield expression is the sole expression
375+
on the right hand side of an assignment statement.
378376

379-
.. index:: object: generator
377+
.. seealso::
378+
379+
:pep:`0255` - Simple Generators
380+
The proposal for adding generators and the :keyword:`yield` statement to Python.
381+
382+
:pep:`0342` - Coroutines via Enhanced Generators
383+
The proposal to enhance the API and syntax of generators, making them
384+
usable as simple coroutines.
380385

386+
:pep:`0380` - Syntax for Delegating to a Subgenerator
387+
The proposal to introduce the :token:`yield_from` syntax, making delegation
388+
to sub-generators easy.
389+
390+
.. index:: object: generator
381391

382392
Generator-iterator methods
383393
^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -395,13 +405,12 @@ is already executing raises a :exc:`ValueError` exception.
395405
.. method:: generator.__next__()
396406

397407
Starts the execution of a generator function or resumes it at the last
398-
executed :keyword:`yield` expression. When a generator function is resumed
399-
with a :meth:`~generator.__next__` method, the current :keyword:`yield`
400-
expression always evaluates to :const:`None`. The execution then continues
401-
to the next :keyword:`yield` expression, where the generator is suspended
402-
again, and the value of the :token:`expression_list` is returned to
403-
:meth:`next`'s caller.
404-
If the generator exits without yielding another value, a :exc:`StopIteration`
408+
executed yield expression. When a generator function is resumed with a
409+
:meth:`~generator.__next__` method, the current yield expression always
410+
evaluates to :const:`None`. The execution then continues to the next yield
411+
expression, where the generator is suspended again, and the value of the
412+
:token:`expression_list` is returned to :meth:`next`'s caller. If the
413+
generator exits without yielding another value, a :exc:`StopIteration`
405414
exception is raised.
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407416
This method is normally called implicitly, e.g. by a :keyword:`for` loop, or
@@ -411,12 +420,12 @@ is already executing raises a :exc:`ValueError` exception.
411420
.. method:: generator.send(value)
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413422
Resumes the execution and "sends" a value into the generator function. The
414-
``value`` argument becomes the result of the current :keyword:`yield`
415-
expression. The :meth:`send` method returns the next value yielded by the
416-
generator, or raises :exc:`StopIteration` if the generator exits without
417-
yielding another value. When :meth:`send` is called to start the generator,
418-
it must be called with :const:`None` as the argument, because there is no
419-
:keyword:`yield` expression that could receive the value.
423+
*value* argument becomes the result of the current yield expression. The
424+
:meth:`send` method returns the next value yielded by the generator, or
425+
raises :exc:`StopIteration` if the generator exits without yielding another
426+
value. When :meth:`send` is called to start the generator, it must be called
427+
with :const:`None` as the argument, because there is no yield expression that
428+
could receive the value.
420429

421430

422431
.. method:: generator.throw(type[, value[, traceback]])
@@ -478,20 +487,6 @@ For examples using ``yield from``, see :ref:`pep-380` in "What's New in
478487
Python."
479488

480489

481-
.. seealso::
482-
483-
:pep:`0255` - Simple Generators
484-
The proposal for adding generators and the :keyword:`yield` statement to Python.
485-
486-
:pep:`0342` - Coroutines via Enhanced Generators
487-
The proposal to enhance the API and syntax of generators, making them
488-
usable as simple coroutines.
489-
490-
:pep:`0380` - Syntax for Delegating to a Subgenerator
491-
The proposal to introduce the :token:`yield_from` syntax, making delegation
492-
to sub-generators easy.
493-
494-
495490
.. _primaries:
496491

497492
Primaries

‎Doc/reference/simple_stmts.rst‎

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@@ -445,53 +445,26 @@ The :keyword:`yield` statement
445445
.. productionlist::
446446
yield_stmt: `yield_expression`
447447

448-
The :keyword:`yield` statement is only used when defining a generator function,
449-
and is only used in the body of the generator function. Using a :keyword:`yield`
450-
statement in a function definition is sufficient to cause that definition to
451-
create a generator function instead of a normal function.
452-
453-
When a generator function is called, it returns an iterator known as a generator
454-
iterator, or more commonly, a generator. The body of the generator function is
455-
executed by calling the :func:`next` function on the generator repeatedly until
456-
it raises an exception.
457-
458-
When a :keyword:`yield` statement is executed, the state of the generator is
459-
frozen and the value of :token:`expression_list` is returned to :meth:`next`'s
460-
caller. By "frozen" we mean that all local state is retained, including the
461-
current bindings of local variables, the instruction pointer, and the internal
462-
evaluation stack: enough information is saved so that the next time :func:`next`
463-
is invoked, the function can proceed exactly as if the :keyword:`yield`
464-
statement were just another external call.
465-
466-
The :keyword:`yield` statement is allowed in the :keyword:`try` clause of a
467-
:keyword:`try` ... :keyword:`finally` construct. If the generator is not
468-
resumed before it is finalized (by reaching a zero reference count or by being
469-
garbage collected), the generator-iterator's :meth:`close` method will be
470-
called, allowing any pending :keyword:`finally` clauses to execute.
471-
472-
When ``yield from <expr>`` is used, it treats the supplied expression as
473-
a subiterator, producing values from it until the underlying iterator is
474-
exhausted.
475-
476-
.. versionchanged:: 3.3
477-
Added ``yield from <expr>`` to delegate control flow to a subiterator
478-
479-
For full details of :keyword:`yield` semantics, refer to the :ref:`yieldexpr`
480-
section.
448+
A :keyword:`yield` statement is semantically equivalent to a :ref:`yield
449+
expression <yieldexpr>`. The yield statement can be used to omit the parentheses
450+
that would otherwise be required in the equivalent yield expression
451+
statement. For example, the yield statements ::
481452

482-
.. seealso::
453+
yield <expr>
454+
yield from <expr>
483455

484-
:pep:`0255` - Simple Generators
485-
The proposal for adding generators and the :keyword:`yield` statement to Python.
456+
are equivalent to the yield expression statements ::
486457

487-
:pep:`0342` - Coroutines via Enhanced Generators
488-
The proposal to enhance the API and syntax of generators, making them
489-
usable as simple coroutines.
458+
(yield <expr>)
459+
(yield from <expr>)
490460

491-
:pep:`0380` - Syntax for Delegating to a Subgenerator
492-
The proposal to introduce the :token:`yield_from` syntax, making delegation
493-
to sub-generators easy.
461+
Yield expressions and statements are only used when defining a :term:`generator`
462+
function, and are only used in the body of the generator function. Using yield
463+
in a function definition is sufficient to cause that definition to create a
464+
generator function instead of a normal function.
494465

466+
For full details of :keyword:`yield` semantics, refer to the
467+
:ref:`yieldexpr` section.
495468

496469
.. _raise:
497470

‎Doc/whatsnew/3.4.rst‎

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@@ -264,6 +264,9 @@ name of the codec responsible for producing the error::
264264
>>> import codecs
265265

266266
>>> codecs.decode(b"abcdefgh", "hex")
267+
Traceback (most recent call last):
268+
File "/usr/lib/python3.4/encodings/hex_codec.py", line 20, in hex_decode
269+
return (binascii.a2b_hex(input), len(input))
267270
binascii.Error: Non-hexadecimal digit found
268271

269272
The above exception was the direct cause of the following exception:
@@ -273,6 +276,11 @@ name of the codec responsible for producing the error::
273276
binascii.Error: decoding with 'hex' codec failed (Error: Non-hexadecimal digit found)
274277

275278
>>> codecs.encode("hello", "bz2")
279+
Traceback (most recent call last):
280+
File "/usr/lib/python3.4/encodings/bz2_codec.py", line 17, in bz2_encode
281+
return (bz2.compress(input), len(input))
282+
File "/usr/lib/python3.4/bz2.py", line 498, in compress
283+
return comp.compress(data) + comp.flush()
276284
TypeError: 'str' does not support the buffer interface
277285

278286
The above exception was the direct cause of the following exception:

‎Lib/asyncio/base_subprocess.py‎

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@@ -114,7 +114,6 @@ def _process_exited(self, returncode):
114114
assert returncode is not None, returncode
115115
assert self._returncode is None, self._returncode
116116
self._returncode = returncode
117-
self._loop._subprocess_closed(self)
118117
self._call(self._protocol.process_exited)
119118
self._try_finish()
120119

‎Lib/asyncio/unix_events.py‎

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@@ -169,9 +169,6 @@ def _make_subprocess_transport(self, protocol, args, shell,
169169
def _child_watcher_callback(self, pid, returncode, transp):
170170
self.call_soon_threadsafe(transp._process_exited, returncode)
171171

172-
def _subprocess_closed(self, transp):
173-
pass
174-
175172

176173
def _set_nonblocking(fd):
177174
flags = fcntl.fcntl(fd, fcntl.F_GETFL)

‎Lib/asyncio/windows_events.py‎

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@@ -178,9 +178,6 @@ def _make_subprocess_transport(self, protocol, args, shell,
178178
yield from transp._post_init()
179179
return transp
180180

181-
def _subprocess_closed(self, transport):
182-
pass
183-
184181

185182
class IocpProactor:
186183
"""Proactor implementation using IOCP."""

‎Lib/codecs.py‎

Lines changed: 6 additions & 7 deletions
Original file line numberDiff line numberDiff line change
@@ -475,22 +475,21 @@ def read(self, size=-1, chars=-1, firstline=False):
475475
# read until we get the required number of characters (if available)
476476
while True:
477477
# can the request be satisfied from the character buffer?
478-
if chars < 0:
479-
if size < 0:
480-
if self.charbuffer:
481-
break
482-
elif len(self.charbuffer) >= size:
483-
break
484-
else:
478+
if chars >= 0:
485479
if len(self.charbuffer) >= chars:
486480
break
481+
elif size >= 0:
482+
if len(self.charbuffer) >= size:
483+
break
487484
# we need more data
488485
if size < 0:
489486
newdata = self.stream.read()
490487
else:
491488
newdata = self.stream.read(size)
492489
# decode bytes (those remaining from the last call included)
493490
data = self.bytebuffer + newdata
491+
if not data:
492+
break
494493
try:
495494
newchars, decodedbytes = self.decode(data, self.errors)
496495
except UnicodeDecodeError as exc:

‎Lib/concurrent/futures/_base.py‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -181,7 +181,8 @@ def as_completed(fs, timeout=None):
181181
182182
Returns:
183183
An iterator that yields the given Futures as they complete (finished or
184-
cancelled).
184+
cancelled). If any given Futures are duplicated, they will be returned
185+
once.
185186
186187
Raises:
187188
TimeoutError: If the entire result iterator could not be generated
@@ -190,11 +191,12 @@ def as_completed(fs, timeout=None):
190191
if timeout is not None:
191192
end_time = timeout + time.time()
192193

194+
fs = set(fs)
193195
with _AcquireFutures(fs):
194196
finished = set(
195197
f for f in fs
196198
if f._state in [CANCELLED_AND_NOTIFIED, FINISHED])
197-
pending = set(fs) - finished
199+
pending = fs - finished
198200
waiter = _create_and_install_waiters(fs, _AS_COMPLETED)
199201

200202
try:

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