new line.
New pvt API function _Py_PrintReferenceAddresses(): Prints only the
addresses and refcnts of the live objects. This is always safe to call,
because it has no dependence on Python's C API.
Py_Finalize(): If envar PYTHONDUMPREFS is set, call (the new)
_Py_PrintReferenceAddresses() right before dumping final pymalloc stats.
We can't print the reprs of the objects here because too much of the
interpreter has been shut down. You need to correlate the addresses
displayed here with the object reprs printed by the earlier
PYTHONDUMPREFS call to _Py_PrintReferences().
New functions:
unsigned long PyInt_AsUnsignedLongMask(PyObject *);
unsigned PY_LONG_LONG) PyInt_AsUnsignedLongLongMask(PyObject *);
unsigned long PyLong_AsUnsignedLongMask(PyObject *);
unsigned PY_LONG_LONG) PyLong_AsUnsignedLongLongMask(PyObject *);
New and changed format codes:
b unsigned char 0..UCHAR_MAX
B unsigned char none **
h unsigned short 0..USHRT_MAX
H unsigned short none **
i int INT_MIN..INT_MAX
I * unsigned int 0..UINT_MAX
l long LONG_MIN..LONG_MAX
k * unsigned long none
L long long LLONG_MIN..LLONG_MAX
K * unsigned long long none
Notes:
* New format codes.
** Changed from previous "range-and-a-half" to "none"; the
range-and-a-half checking wasn't particularly useful.
New test test_getargs2.py, to verify all this.
PYTHONDUMPREFS output after most teardown. Attempts to use
PYTHONDUMPREFS with the Zope3 test suite died with Py_FatalError(),
since _Py_PrintReferences() can end up executing arbitrary Python code
(for objects that override __repr__), and that requires an intact
interpreter.
even farther down, to just before the call to
_PyObject_DebugMallocStats(). This required the following changes:
- pystate.c, PyThreadState_GetDict(): changed not to raise an
exception or issue a fatal error when no current thread state is
available, but simply return NULL without raising an exception
(ever).
- object.c, Py_ReprEnter(): when PyThreadState_GetDict() returns NULL,
don't raise an exception but return 0. This means that when
printing a container that's recursive, printing will go on and on
and on. But that shouldn't happen in the case we care about (see
first bullet).
- Updated Misc/NEWS and Doc/api/init.tex to reflect changes to
PyThreadState_GetDict() definition.
the code erroneously decrefed the istep argument in an error case. This
caused a co_consts tuple to lose a float constant prematurely, which
eventually caused gc to try executing static data in floatobject.c (don't
ask <wink>). So reworked this extensively to ensure refcount correctness.
- range() now works even if the arguments are longs with magnitude
larger than sys.maxint, as long as the total length of the sequence
fits. E.g., range(2**100, 2**101, 2**100) is the following list:
[1267650600228229401496703205376L]. (SF patch #707427.)
return. Setting an exception can mess with the exception state, and
continuing is definitely wrong (since type is dereferenced later on).
Some code that calls this seems to be prepared for a NULL exception
type, so let's be safe rather than sorry and simply assume there's
nothing to normalize in this case.
Adds a single function to improve generated bytecode. Has a single line
attachment point, so it is completely de-coupled from both the compiler
and ceval.c.
Makes three simple transforms that do not require a basic block analysis
or re-ordering of code. Gives improved timings on pystone, pybench,
and any code using either "while 1" or "x,y=y,x".
Arranged that all the objects exposed by __builtin__ appear in the list
of all objects. I basically peed away two days tracking down a mystery
leak in sys.gettotalrefcount() in a ZODB app (== tons of code), because
the object leaking the references didn't appear in the sys.getobjects(0)
list. The object happened to be False. Now False is in the list, along
with other popular & previously missing leak candidates (like None).
Alas, we still don't have a choke point covering *all* Python objects,
so the list of all objects may still be incomplete.
variables to store internal data. As a result, any atempts to use the
unicode system with multiple active interpreters, or successive
interpreter executions, would fail.
Now that information is stored into members of the PyInterpreterState
structure.
Added two predictions:
GET_ITER --> FOR_ITER
FOR_ITER --> STORE_FAST or UNPACK_SEQUENCE
Improves timings on pybench and timeit.py. Pystone results are neutral.
Applied to common cases:
COMPARE_OP is often followed by a JUMP_IF.
JUMP_IF is usually followed by POP_TOP.
Shows improved timings on PyStone, PyBench, and specific tests
using timeit.py:
python timeit.py -s "x=1" "if x==1: pass"
python timeit.py -s "x=1" "if x==2: pass"
python timeit.py -s "x=1" "if x: pass"
python timeit.py -s "x=100" "while x!=1: x-=1"
Potential future candidates:
GET_ITER predicts FOR_ITER
FOR_ITER predicts STORE_FAST or UNPACK_SEQUENCE
Also, applied missing goto fast_next_opcode to DUP_TOPX.
My previous patches should have used fast_next_opcode
in a few places instead of continue.
Also, applied one PyInt_AS_LONG macro in a place where
the type had already been checked.
rarely needed, but can sometimes be useful to release objects
referenced by the traceback held in sys.exc_info()[2]. (SF patch
#693195.) Thanks to Kevin Jacobs!
import warnings.py _after_ site.py has run. This ensures that site.py
is again the first .py to be imported, giving it back full control over
sys.path.
with an indented code block but no newline would raise SyntaxError.
This would have been a four-line change in parsetok.c... Except
codeop.py depends on this behavior, so a compilation flag had to be
invented that causes the tokenizer to revert to the old behavior;
this required extra changes to 2 .h files, 2 .c files, and 2 .py
files. (Fixes SF bug #501622.)
mostly from SF patch #683257, but I had to change unlock_import() to
return an error value to avoid fatal error.
Should this be backported? The patch requested this, but it's a new
feature.
"Unsigned" (i.e., positive-looking, but really negative) hex/oct
constants with a leading minus sign are once again properly negated.
The micro-optimization for negated numeric constants did the wrong
thing for such hex/oct constants. The patch avoids the optimization
for all hex/oct constants.
This needs to be backported to Python 2.2!
object is not a real str or unicode but an instance
of a subclass, construct the output via looping
over __getitem__. This guarantees that the result
is the same for function==None and function==lambda x:x
This doesn't happen for tuples, because filtertuple()
uses PyTuple_GetItem().
(This was discussed on SF bug #665835).
-DCALL_PROFILE: Count the number of function calls executed.
When this symbol is defined, the ceval mainloop and helper functions
count the number of function calls made. It keeps detailed statistics
about what kind of object was called and whether the call hit any of
the special fast paths in the code.
Optimization:
When we take the fast_function() path, which seems to be taken for
most function calls, and there is minimal frame setup to do, avoid
call PyEval_EvalCodeEx(). The eval code ex function does a lot of
work to handle keywords args and star args, free variables,
generators, etc. The inlined version simply allocates the frame and
copies the arguments values into the frame.
The optimization gets a little help from compile.c which adds a
CO_NOFREE flag to code objects that don't have free variables or cell
variables. This change allows fast_function() to get into the fast
path with fewer tests.
I measure a couple of percent speedup in pystone with this change, but
there's surely more that can be done.
blindly assumed that tp_as_sequence->sq_item always returns
a str or unicode object. This might fail with str or unicode
subclasses.
This patch checks whether the object returned from __getitem__
is a str/unicode object and raises a TypeError if not (and
the filter function returned true).
Furthermore the result for __getitem__ can be more than one
character long, so checks for enough memory have to be done.
__module__ is the string name of the module the function was defined
in, just like __module__ of classes. In some cases, particularly for
C functions, the __module__ may be None.
Change PyCFunction_New() from a function to a macro, but keep an
unused copy of the function around so that we don't change the binary
API.
Change pickle's save_global() to use whichmodule() if __module__ is
None, but add the __module__ logic to whichmodule() since it might be
used outside of pickle.
Make the code slightly shorter, faster, and easier to
read.
* Eliminate unused DUP_TOPX code for x==1.
compile.c always generates DUP_TOP instead.
* Since only two cases remain for DUP_TOPX, replace
the switch-case with if-elseif.
* The in-lined integer compare does a CheckExact on
both arguments. Since the second is a little more
likely to fail, test it first.
* The switch-case for IS/IS_NOT and IN/NOT_IN can
separate the regular and inverted cases with no
additional work. For all four paths, saves a test and
jump.
the AEDesc data shouldn't be disposed when the Python object is.
Added a C call AEDesc_NewBorrowed() to create these objects and a Python
method old=AEDesc.AutoDispose(onoff) to change auto-dispose state.
The two are semantically equivalent, but the first triggered a compiler
warning about an unused variable. Note, the preceding steps had already
accessed and decreffed the variable so the reference counts were fine.
parameter being either four or five. Currently, compile.c does not
generate calls with a parameter higher than three.
May have to be reverted if the second alpha or beta shakes out some
other tool generating this op code with a parameter of four or five.
Replaced groups of pushes and pops with indexed access to the stack and
a single adjustment (if needed) to the stacklevel.
Avoids scores of unnecessary increments and decrements to the stackpointer.
Removes unnecessary sequential dependencies so that the compiler has more
freedom for optimizations. Frees the processor for more parallel and
pipelined execution by using mostly read-only access and having few pointer
adjustments just prior to a read or write.
This fixes the problem on Windows - that's the only system where I can
test it.
It leaves sys.argv alone and only changes sys.path[0] to an absolute
pathname.
A variety of changes from Michael Hudson to get the compiler working
with 2.3. The primary change is the handling of SET_LINENO:
# The set_lineno() function and the explicit emit() calls for
# SET_LINENO below are only used to generate the line number table.
# As of Python 2.3, the interpreter does not have a SET_LINENO
# instruction. pyassem treats SET_LINENO opcodes as a special case.
A few other small changes:
- Remove unused code from pycodegen and pyassem.
- Fix error handling in parsermodule. When PyParser_SimplerParseString()
fails, it sets an exception with detailed info. The parsermodule
was clobbering that exception and replacing it was a generic
"could not parse string" exception. Keep the original exception.
I can't test this on the snake farm (no aix box is working).
This change works for the submitter seems correct.
Can anybody test this on 32- and 64- bit AIX?
Initialize the small integers and __builtins__ in startup.
This removes some if conditions.
Change XDECREF to DECREF for values which shouldn't be NULL.
- new import hooks in import.c, exposed in the sys module
- new module called 'zipimport'
- various changes to allow bootstrapping from zip files
I hope I didn't break the Windows build (or anything else for that
matter), but then again, it's been sitting on sf long enough...
Regarding the latest discussions on python-dev: zipimport sets
pkg.__path__ as specified in PEP 273, and likewise, sys.path item such as
/path/to/Archive.zip/subdir/ are supported again.
Obtain cleaner coding and a system wide
performance boost by using the fast, pre-parsed
PyArg_Unpack function instead of PyArg_ParseTuple
function which is driven by a format string.
[#448679] Left to right
* Python/compile.c
(com_dictmaker): Reordered evaluation of dictionaries to follow strict
LTR evaluation.
* Lib/compiler/pycodegen.py
(CodeGenerator.visitDict): Reordered evaluation of dictionaries to
follow strict LTR evaluation.
* Doc/ref/ref5.tex
Documented the general LTR evaluation order idea.
* Misc/NEWS
Documented change in evaluation order of dictionaries.
supported as the second argument. This has the same meaning as
for isinstance(), i.e. issubclass(X, (A, B)) is equivalent
to issubclass(X, A) or issubclass(X, B). Compared to isinstance(),
this patch does not search the tuple recursively for classes, i.e.
any entry in the tuple that is not a class, will result in a
TypeError.
This closes SF patch #649608.
Py_Init crash". refchain cannot be cleared because objects can live across
Py_Finalize() and Py_Initialize() if they are kept alive by circular
references.
dialogs are now stored in Mac/Lib, and loaded on demand through macresource.
Not only does this simplify a MacPython based on Apple's Python, but
it also makes Mac error codes come out symbolically when running command
line python (if you have Mac/Lib in your path).
The resource files are copied from Mac/Resources. The old ones will disappear
after the OS9 build procedure has been adjusted.
sys.getwindowsversion() on Windows (new enahanced Tim-proof <wink>
version), and fix test_pep277.py in a few minor ways.
Including doc and NEWS entries.
all along. Before instr_lb tended to be too high.
I don't think this actually makes any difference, given what the compiler
produces, but it makes me a bit happier.
patch #617312, both on the trunk and the 22-maint branch.
Also added a test case, and ported the test_trace I wrote for HEAD
to 2.2.2 (with all those horrible extra 'line' events ;-).
The switch in Exception__str__ didn't clear the error if
PySequence_Size() raised an exception. Added a case -1 which clears
the error and falls through to the default case.
Definite backport candidate (this dates all the way to Python 2.0).
than when this interval was first established. Checking too frequently just
adds needless overhead because most of the time there is nothing to do and
no other threads ready to run.
globals, _Py_Ticker and _Py_CheckInterval. This also implements Jeremy's
shortcut in Py_AddPendingCall that zeroes out _Py_Ticker. This allows the
test in the main loop to only test a single value.
The gory details are at
http://python.org/sf/602191
Use a slightly different strategy to determine when not to call the line
trace function. This removes the need for the RETURN_NONE opcode, so
that's gone again. Update docs and comments to match.
Thanks to Neal and Armin!
Also add a test suite. This should have come with the original patch...
in LOAD_GLOBAL. Besides saving a C function call, it saves checks
whether f_globals and f_builtins are dicts, and extracting and testing
the string object's hash code is done only once. We bail out of the
inlining if the name is not exactly a string, or when its hash is -1;
because of interning, neither should ever happen. I believe interning
guarantees that the hash code is set, and I believe that the 'names'
tuple of a code object always contains interned strings, but I'm not
assuming that -- I'm simply testing hash != -1.
On my home machine, this makes a pystone variant with new-style
classes and slots run at the same speed as classic pystone! (With
new-style classes but without slots, it is still a lot slower.)
Also, don't handle METH_OLDARGS on the fast path. All the interesting
builtins have been converted to use METH_NOARGS, METH_O, or
METH_VARARGS.
Result is another 1-2% speedup. If I can cobble together 10 of these,
it might make a difference.
This makes the code much easier to ready, because it is at a sane
indentation level. On my box this shows a 1-2% speedup, which means
nothing, except that I'm not going to worry about the performance
effects of the change.
nothing special done if keyword arguments were present, so test for
that earlier and fall through to the normal case if there are any.
This ought to slow down CFunction calls with keyword args, but I don't
care; it's a tiny (1%) improvement for pystone.
- Use PyObject_Call() instead of PyEval_CallObject(), saves several
layers of calls and checks.
- Pre-allocate the argument tuple rather than calling Py_BuildValue()
each time round the loop.
- For filter(None, seq), avoid an INCREF and a DECREF.
warning for 'global None', but that's either accompanied by an
assignment to None, which will trigger a warning, or not, in which
case it's harmless. :-)
[ 587993 ] SET_LINENO killer
Remove SET_LINENO. Tracing is now supported by inspecting co_lnotab.
Many sundry changes to document and adapt to this change.
currently return inconsistent results for ints and longs; in
particular: hex/oct/%u/%o/%x/%X of negative short ints, and x<<n that
either loses bits or changes sign. (No warnings for repr() of a long,
though that will also change to lose the trailing 'L' eventually.)
This introduces some warnings in the test suite; I'll take care of
those later.
Change the parser and compiler to use PyMalloc.
Only the files implementing processes that will request memory
allocations small enough for PyMalloc to be a win have been
changed, which are:-
- Python/compile.c
- Parser/acceler.c
- Parser/node.c
- Parser/parsetok.c
This augments the aggressive overallocation strategy implemented by
Tim Peters in PyNode_AddChild() [Parser/node.c], in reducing the
impact of platform malloc()/realloc()/free() corner case behaviour.
Such corner cases are known to be triggered by test_longexp and
test_import.
Jeremy Hylton, in accepting this patch, recommended this as a
bugfix candidate for 2.2. While the changes to Python/compile.c
and Parser/node.c backport easily (and could go in), the changes
to Parser/acceler.c and Parser/parsetok.c require other not
insignificant changes as a result of the differences in the memory
APIs between 2.3 and 2.2, which I'm not in a position to work
through at the moment. This is a pity, as the Parser/parsetok.c
changes are the most important after the Parser/node.c changes, due
to the size of the memory requests involved and their frequency.
actual script to run in case we are running from an applet. If we are indeed
running an applet we skip the normal option processing leaving it all to the
applet code.
This allows us to get use the normal python binary in the Python.app bundle,
giving us all the normal command line options through PythonLauncher while
still allowing Python.app to be used as the template for building applets.
Consequently, pythonforbundle is gone, and Mac/Python/macmain.c isn't used
on OSX anymore.
See there for a description.
Added test case.
Bugfix candidate for 2.2.x, not sure about previous versions:
probably low priority, because virtually no one runs debug builds.
PyErr_SetExcFromWindowsErr(), PyErr_SetExcFromWindowsErrWithFilename().
Similar to PyErr_SetFromWindowsErrWithFilename() and
PyErr_SetFromWindowsErr(), but they allow to specify
the exception type to raise. Available on Windows.
See SF patch #576458.
is slow things down unnecessarily and make tracing much more verbose.
Something like
def f(n):
return [i for i in range(n) if i%2]
should have at most two SET_LINENO instructions, not four. When tracing,
the current line number should be printed once, not 2*n+1 times.
The staticforward define was needed to support certain broken C
compilers (notably SCO ODT 3.0, perhaps early AIX as well) botched the
static keyword when it was used with a forward declaration of a static
initialized structure. Standard C allows the forward declaration with
static, and we've decided to stop catering to broken C compilers. (In
fact, we expect that the compilers are all fixed eight years later.)
I'm leaving staticforward and statichere defined in object.h as
static. This is only for backwards compatibility with C extensions
that might still use it.
XXX I haven't updated the documentation.
more trivial lexical helper macros so that uses of these guys expand
to nothing at all when they're not enabled. This should help sub-
standard compilers that can't do a good job of optimizing away the
previous "(void)0" expressions.
Py_DECREF: There's only one definition of this now. Yay! That
was that last one in the family defined multiple times in an #ifdef
maze.
Py_FatalError(): Changed the char* signature to const char*.
_Py_NegativeRefcount(): New helper function for the Py_REF_DEBUG
expansion of Py_DECREF. Calling an external function cuts down on
the volume of generated code. The previous inline expansion of abort()
didn't work as intended on Windows (the program often kept going, and
the error msg scrolled off the screen unseen). _Py_NegativeRefcount
calls Py_FatalError instead, which captures our best knowledge of
how to abort effectively across platforms.
that have taken me "too long" to reverse-engineer over the years.
Vastly reduced the nesting level and redundancy of #ifdef-ery.
Took a light stab at repairing comments that are no longer true.
sys_gettotalrefcount(): Changed to enable under Py_REF_DEBUG.
It was enabled under Py_TRACE_REFS, which was much heavier than
necessary. sys.gettotalrefcount() is now available in a
Py_REF_DEBUG-only build.
This patch enhances Python/import.c/find_module() so
that unicode objects found in sys.path will be treated
as legal directory names (The current code ignores
anything that is not a str). The unicode name is
converted to str using Py_FileSystemDefaultEncoding.
These built-in functions are replaced by their (now callable) type:
slice()
buffer()
and these types can also be called (but have no built-in named
function named after them)
classobj (type name used to be "class")
code
function
instance
instancemethod (type name used to be "instance method")
The module "new" has been replaced with a small backward compatibility
placeholder in Python.
A large portion of the patch simply removes the new module from
various platform-specific build recipes. The following binary Mac
project files still have references to it:
Mac/Build/PythonCore.mcp
Mac/Build/PythonStandSmall.mcp
Mac/Build/PythonStandalone.mcp
[I've tweaked the code layout and the doc strings here and there, and
added a comment to types.py about StringTypes vs. basestring. --Guido]
Write 4 bytes for co_stacksize, etc. to prevent writing out
bad .pyc files which can cause a crash when read back in.
(I forgot that frozen needs to be updated too for the test.)
This was a simple typo. Strange that the compiler didn't catch it!
Instead of WHY_CONTINUE, two tests used CONTINUE_LOOP, which isn't a
why_code at all, but an opcode; but even though 'why' is declared as
an enum, comparing it to an int is apparently not even worth a
warning -- not in gcc, and not in VC++. :-(
Will fix in 2.2 too.
get_file() must convert 'U' to "r" PY_STDIOTEXTMODE before calling
fopen().
imp_load_module() must accept 'r' or 'U' or something with '+'.
Also reflow some long lines.
for 'str' and 'unicode', and can be used instead of
types.StringTypes, e.g. to test whether something is "a string":
isinstance(x, string) is True for Unicode and 8-bit strings. This
is an abstract base class and cannot be instantiated directly.
The old syntax suggested that a trailing comma was OK inside backticks,
but in fact (due to ideosyncrasies of pgen) it was not. Fix the grammar
to avoid the ambiguity. Fred: you may want to update the refman.
[ 558249 ] softspace vs --disable-unicode
And #endif was in the wrong place.
Bugfix candidate, almost surely.
I think I will embark on squashing test failures in --disable-unicode builds --
a Real Bug was hiding under them.
don't understand how this function works, also beefed up the docs. The
most common usage error is of this form (often spread out across gotos):
if (_PyString_Resize(&s, n) < 0) {
Py_DECREF(s);
s = NULL;
goto outtahere;
}
The error is that if _PyString_Resize runs out of memory, it automatically
decrefs the input string object s (which also deallocates it, since its
refcount must be 1 upon entry), and sets s to NULL. So if the "if"
branch ever triggers, it's an error to call Py_DECREF(s): s is already
NULL! A correct way to write the above is the simpler (and intended)
if (_PyString_Resize(&s, n) < 0)
goto outtahere;
Bugfix candidate.
The SIGXFSZ signal is sent when the maximum file size limit is
exceeded (RLIMIT_FSIZE). Apparently, it is also sent when the 2GB
file limit is reached on platforms without large file support.
The default action for SIGXFSZ is to terminate the process and dump
core. When it is ignored, the system call that caused the limit to be
exceeded returns an error and sets errno to EFBIG. Python
always checks errno on I/O syscalls, so there is nothing to do with
the signal.
+ Redirect PyMem_{Del, DEL} to the object allocator's free() when
pymalloc is enabled. Needed so old extensions can continue to
mix PyObject_New with PyMem_DEL.
+ This implies that pgen needs to be able to see the PyObject_XYZ
declarations too. pgenheaders.h now includes Python.h. An
implication is that I expect obmalloc.o needs to get linked into
pgen on non-Windows boxes.
+ When PYMALLOC_DEBUG is defined, *all* Py memory API functions
now funnel through the debug allocator wrapper around pymalloc.
This is the default in a debug build.
+ That caused compile.c to fail: it indirectly mixed PyMem_Malloc
with raw platform free() in one place. This is verbotten.
Highlights: import and friends will understand any of \r, \n and \r\n
as end of line. Python file input will do the same if you use mode 'U'.
Everything can be disabled by configuring with --without-universal-newlines.
See PEP278 for details.
Added code to call this when PYMALLOC_DEBUG is enabled, and envar
PYTHONMALLOCSTATS is set, whenever a new arena is obtained and once
late in the Python shutdown process.
PEP 285. Everything described in the PEP is here, and there is even
some documentation. I had to fix 12 unit tests; all but one of these
were printing Boolean outcomes that changed from 0/1 to False/True.
(The exception is test_unicode.py, which did a type(x) == type(y)
style comparison. I could've fixed that with a single line using
issubtype(x, type(y)), but instead chose to be explicit about those
places where a bool is expected.
Still to do: perhaps more documentation; change standard library
modules to return False/True from predicates.
SF bug 535905 (Evil Trashcan and GC interaction).
The SETLOCAL() macro should not DECREF the local variable in-place and
then store the new value; it should copy the old value to a temporary
value, then store the new value, and then DECREF the temporary value.
This is because it is possible that during the DECREF the frame is
accessed by other code (e.g. a __del__ method or gc.collect()) and the
variable would be pointing to already-freed memory.
BUGFIX CANDIDATE!
descriptor, as used for the tp_methods slot of a type. These new flag
bits are both optional, and mutually exclusive. Most methods will not
use either. These flags are used to create special method types which
exist in the same namespace as normal methods without having to use
tedious construction code to insert the new special method objects in
the type's tp_dict after PyType_Ready() has been called.
If METH_CLASS is specified, the method will represent a class method
like that returned by the classmethod() built-in.
If METH_STATIC is specified, the method will represent a static method
like that returned by the staticmethod() built-in.
These flags may not be used in the PyMethodDef table for modules since
these special method types are not meaningful in that case; a
ValueError will be raised if these flags are found in that context.
This fixes the symptom, but PRINT_ITEM has no way to know what (if
anything) PyFile_WriteObject() writes unless the object being printed
is a string. When the object isn't a string, this fix retains the
guess that softspace should be set after PyFile_WriteObject().
We might want to say that it's the job of filelike-object write methods
to leave the file's softspace in the correct state. That would probably
be better -- but everyone relies on PRINT_ITEM to guess for them now.