* Speed-up "x in y" where x has more than one character.
The existing code made excessive calls to the expensive memcmp() function.
The new code uses memchr() to rapidly find a start point for memcmp().
In addition to knowing that the first character is a match, the new code
also checks that the last character is a match. This significantly reduces
the incidence of false starts (saving memcmp() calls and making quadratic
behavior less likely).
Improves the timings on:
python -m timeit -r7 -s"x='a'*1000" "'ab' in x"
python -m timeit -r7 -s"x='a'*1000" "'bc' in x"
Once this code has proven itself, then string_find_internal() should refer
to it rather than running its own version. Also, something similar may
apply to unicode objects.
(Patch contributed by Nick Coghlan.)
Now joining string subtypes will always return a string.
Formerly, if there were only one item, it was returned unchanged.
hack: it would resize *interned* strings in-place! This occurred because
their reference counts do not have their expected value -- stringobject.c
hacks them. Mea culpa.
interning were not clear here -- a subclass could be mutable, for
example -- and had bugs. Explicitly interning a subclass of string
via intern() will raise a TypeError. Internal operations that attempt
to intern a string subclass will have no effect.
Added a few tests to test_builtin that includes the old buggy code and
verifies that calls like PyObject_SetAttr() don't fail. Perhaps these
tests should have gone in test_string.
bit by checking the value of UCHAR_MAX in Include/Python.h. There was a
check in Objects/stringobject.c. Remove that. (Note that we don't define
UCHAR_MAX if it's not defined as the old test did.)
and left shifts. (Thanks to Kalle Svensson for SF patch 849227.)
This addresses most of the remaining semantic changes promised by
PEP 237, except for repr() of a long, which still shows the trailing
'L'. The PEP appears to promise warnings for operations that
changed semantics compared to Python 2.3, but this is not
implemented; we've suffered through enough warnings related to
hex/oct literals and I think it's best to be silent now.
* Doc - add doc for when functions were added
* UserString
* string object methods
* string module functions
'chars' is used for the last parameter everywhere.
These changes will be backported, since part of the changes
have already been made, but they were inconsistent.
types. The special handling for these can now be removed from save_newobj().
Add some testing for this.
Also add support for setting the 'fast' flag on the Python Pickler class,
which suppresses use of the memo.
Christian Tismer pointed out the high cost of the loop overhead and
function call overhead for 'c' * n where n is large. Accordingly,
the new code only makes lg2(n) loops.
Interestingly, 'c' * 1000 * 1000 ran a bit faster with old code. At some
point, the loop and function call overhead became cheaper than invalidating
the cache with lengthy memcpys. But for more typical sizes of n, the new
code runs much faster and for larger values of n it runs only a bit slower.
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.
When mwh added extended slicing, strings and unicode became mappings.
Thus, dict was set which prevented an error when doing:
newstr = 'format without a percent' % string_value
This fix raises an exception again when there are no formats
and % with a string value.
'%2147483647d' % -123 segfaults. This was because an integer overflow
in a comparison caused the string resize to be skipped. After fixing
the overflow, this could call _PyString_Resize() with a negative size,
so I (1) test for that and raise MemoryError instead; (2) also added a
test for negative newsize to _PyString_Resize(), raising SystemError
as for all bad arguments.
An identical bug existed in unicodeobject.c, of course.
Will backport to 2.2.2.
Also fixed an error message -- %s argument has non-string str()
doesn't make sense for %r, so the error message now differentiates
between %s and %r.
because PyObject_Repr() and PyObject_Str() ensure that this can never
happen. Added a helpful comment instead.
sees a Unicode argument. Unfortunately this test was also executed
for %r, because %s and %r share almost all of their code. This meant
that, if u is a unicode object while repr(u) is an 8-bit string
containing ASCII characters, '%r' % u is a *unicode* string containing
only ASCII characters!
Fixed by executing the test only for %s.
Also fixed an error message -- %s argument has non-string str()
doesn't make sense for %r, so the error message now differentiates
between %s and %r.
of PyString_DecodeEscape(). This prevents a call to
_PyString_Resize() for the empty string, which would
result in a PyErr_BadInternalCall(), because the
empty string has more than one reference.
This closes SF bug http://www.python.org/sf/603937
possible. This always called PyUnicode_Check() and PyString_Check(),
at least one of which would call PyType_IsSubtype(). Also, this would
call PyString_Size() on known string objects.
interning. I modified Oren's patch significantly, but the basic idea
and most of the implementation is unchanged. Interned strings created
with PyString_InternInPlace() are now mortal, and you must keep a
reference to the resulting string around; use the new function
PyString_InternImmortal() to create immortal interned strings.
comments everywhere that bugged me: /* Foo is inlined */ instead of
/* Inline Foo */. Somehow the "is inlined" phrase always confused me
for half a second (thinking, "No it isn't" until I added the missing
"here"). The new phrase is hopefully unambiguous.
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.
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.
helper macros to something saner, and used them appropriately in other
files too, to reduce #ifdef blocks.
classobject.c, instance_dealloc(): One of my worst Python Memories is
trying to fix this routine a few years ago when COUNT_ALLOCS was defined
but Py_TRACE_REFS wasn't. The special-build code here is way too
complicated. Now it's much simpler. Difference: in a Py_TRACE_REFS
build, the instance is no longer in the doubly-linked list of live
objects while its __del__ method is executing, and that may be visible
via sys.getobjects() called from a __del__ method. Tough -- the object
is presumed dead while its __del__ is executing anyway, and not calling
_Py_NewReference() at the start allows enormous code simplification.
typeobject.c, call_finalizer(): The special-build instance_dealloc()
pain apparently spread to here too via cut-'n-paste, and this is much
simpler now too. In addition, I didn't understand why this routine
was calling _PyObject_GC_TRACK() after a resurrection, since there's no
plausible way _PyObject_GC_UNTRACK() could have been called on the
object by this point. I suspect it was left over from pasting the
instance_delloc() code. Instead asserted that the object is still
tracked. Caution: I suspect we don't have a test that actually
exercises the subtype_dealloc() __del__-resurrected-me code.
[ 400998 ] experimental support for extended slicing on lists
somewhat spruced up and better tested than it was when I wrote it.
Includes docs & tests. The whatsnew section needs expanding, and arrays
should support extended slices -- later.
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.
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.
http://www.python.org/sf/444708
This adds the optional argument for str.strip
to unicode.strip too and makes it possible
to call str.strip with a unicode argument
and unicode.strip with a str argument.
Add a method zfill to str, unicode and UserString and change
Lib/string.py accordingly.
This activates the zfill version in unicodeobject.c that was
commented out and implements the same in stringobject.c. It also
adds the test for unicode support in Lib/string.py back in and
uses repr() instead() of str() (as it was before Lib/string.py 1.62)
Add optional arg to string methods strip(), lstrip(), rstrip().
The optional arg specifies characters to delete.
Also for UserString.
Still to do:
- Misc/NEWS
- LaTeX docs (I did the docstrings though)
- Unicode methods, and Unicode support in the string methods.
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.
Objects/
fileobject.c
stringobject.c
unicodeobject.c
This commit doesn't include the cleanup patches for stringobject.c and
unicodeobject.c which are shown separately in the patch manager. Those
patches will be regenerated and applied in a subsequent commit, so as
to preserve a fallback position (this commit to those files).
PyString_FromString():
Since the length of the string is already being stored in size,
changed the strcpy() to a memcpy() for a small speed improvement.
Add a missing DECREF in an obscure corner. If the str() or repr() of
an object passed to a string interpolation -- e.g. "%s" % obj --
returns a non-string, the returned object was leaked.
Repair an indentation glitch.
Replace a bunch of PyString_AsString() calls (and their ilk) with
macros.
response to a message by Laura Creighton on c.l.py. E.g.
>>> 0+''
TypeError: unsupported operand types for +: 'int' and 'str'
(previously this did not mention the operand types)
>>> ''+0
TypeError: cannot concatenate 'str' and 'int' objects
object.c, PyObject_Str: Don't try to optimize anything except exact
string objects here; in particular, let str subclasses go thru tp_str,
same as non-str objects. This allows overrides of tp_str to take
effect.
stringobject.c:
+ string_print (str's tp_print): If the argument isn't an exact string
object, get one from PyObject_Str.
+ string_str (str's tp_str): Make a genuine-string copy of the object if
it's of a proper str subclass type. str() applied to a str subclass
that doesn't override __str__ ends up here.
test_descr.py: New str_of_str_subclass() test.
many types were subclassable but had a xxx_dealloc function that
called PyObject_DEL(self) directly instead of deferring to
self->ob_type->tp_free(self). It is permissible to set tp_free in the
type object directly to _PyObject_Del, for non-GC types, or to
_PyObject_GC_Del, for GC types. Still, PyObject_DEL was a tad faster,
so I'm fearing that our pystone rating is going down again. I'm not
sure if doing something like
void xxx_dealloc(PyObject *self)
{
if (PyXxxCheckExact(self))
PyObject_DEL(self);
else
self->ob_type->tp_free(self);
}
is any faster than always calling the else branch, so I haven't
attempted that -- however those types whose own dealloc is fancier
(int, float, unicode) do use this pattern.
Unknown whether this fixes it.
- stringobject.c, PyString_FromFormatV: don't assume that va_list is of
a type that can be copied via an initializer.
- errors.c, PyErr_Format: add a va_end() to balance the va_start().
with the same value instead. This ensures that a string (or string
subclass) object's ob_sinterned pointer is always a str (or NULL), and
that the dict of interned strings only has strs as keys.
+ These were leaving the hash fields at 0, which all string and unicode
routines believe is a legitimate hash code. As a result, hash() applied
to str and unicode subclass instances always returned 0, which in turn
confused dict operations, etc.
+ Changed local names "new"; no point to antagonizing C++ compilers.
subclasses, all "the usual" ones (slicing etc), plus replace, translate,
ljust, rjust, center and strip. I don't know how to be sure they've all
been caught.
Question: Should we complain if someone tries to intern an instance of
a string subclass? I hate to slow any code on those paths.
Raymond Hettinger
Michael W. Hudson
Armin Rigo
Jeremy Hylton
Marc-André Lemburg
Tim Peters
Martin v. Löwis
Hye-Shik Chang
Skip Montanaro
Guido van Rossum
Fred Drake
Walter Dörwald
Neal Norwitz
Neil Schemenauer
Barry Warsaw
Andrew MacIntyre