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.
Big Hammer to implement -Qnew as PEP 238 says it should work (a global
option affecting all instances of "/").
pydebug.h, main.c, pythonrun.c: define a private _Py_QnewFlag flag, true
iff -Qnew is passed on the command line. This should go away (as the
comments say) when true division becomes The Rule. This is
deliberately not exposed to runtime inspection or modification: it's
a one-way one-shot switch to pretend you're using Python 3.
ceval.c: when _Py_QnewFlag is set, treat BINARY_DIVIDE as
BINARY_TRUE_DIVIDE.
test_{descr, generators, zipfile}.py: fiddle so these pass under
-Qnew too. This was just a matter of s!/!//! in test_generators and
test_zipfile. test_descr was trickier, as testbinop() is passed
assumptions that "/" is the same as calling a "__div__" method; put
a temporary hack there to call "__truediv__" instead when the method
name is "__div__" and 1/2 evaluates to 0.5.
Three standard tests still fail under -Qnew (on Windows; somebody
please try the Linux tests with -Qnew too! Linux runs a whole bunch
of tests Windows doesn't):
test_augassign
test_class
test_coercion
I can't stay awake longer to stare at this (be my guest). Offhand
cures weren't obvious, nor was it even obvious that cures are possible
without major hackery.
Question: when -Qnew is in effect, should calls to __div__ magically
change into calls to __truediv__? See "major hackery" at tail end of
last paragraph <wink>.
horridly inefficient hack in regrtest's Compare class, but it's about as
clean as can be: regrtest has to set up the Compare instance before
importing a test module, and by the time the module *is* imported it's too
late to change that decision. The good news is that the more tests we
convert to unittest and doctest, the less the inefficiency here matters.
Even now there are few tests with large expected-output files (the new
cost here is a Python-level call per .write() when there's an expected-
output file).
bag. It's clearly wrong for classic classes, at heart because a classic
class doesn't have a __class__ attribute, and I'm unclear on whether
that's feature or bug. I'll repair this once I find out (in the
meantime, dir() applied to classic classes won't find the base classes,
while dir() applied to a classic-class instance *will* find the base
classes but not *their* base classes).
Please give the new dir() a try and see whether you love it or hate it.
The new dir([]) behavior is something I could come to love. Here's
something to hate:
>>> class C:
... pass
...
>>> c = C()
>>> dir(c)
['__doc__', '__module__']
>>>
The idea that an instance has a __doc__ attribute is jarring (of course
it's really c.__class__.__doc__ == C.__doc__; likewise for __module__).
OTOH, the code already has too many special cases, and dir(x) doesn't
have a compelling or clear purpose when x isn't a module.
that info to code dynamically compiled *by* code compiled with generators
enabled. Doesn't yet work because there's still no way to tell the parser
that "yield" is OK (unlike nested_scopes, the parser has its fingers in
this too).
Replaced PyEval_GetNestedScopes by a more-general
PyEval_MergeCompilerFlags. Perhaps I should not have? I doubted it was
*intended* to be part of the public API, so just did.
solver. In conjunction, they easily found a tour of a 200x200 board:
that's 200**2 == 40,000 levels of backtracking. Explicitly resumable
generators allow that to be coded as easily as a recursive solver (easier,
actually, because different levels can use level-customized algorithms
without pain), but without blowing the stack. Indeed, I've never written
an exhaustive Tour solver in any language before that can handle boards so
large ("exhaustive" == guaranteed to find a solution if one exists, as
opposed to probabilistic heuristic approaches; of course, the age of the
universe may be a blip in the time needed!).
examples of use. These poke stuff not specifically targeted before, incl.
recursive local generators relying on nested scopes, ditto but also
inside class methods and rebinding instance vars, and anonymous
partially-evaluated generators (the N-Queens solver creates a different
column-generator for each row -- AFAIK this is my invention, and it's
really pretty <wink>). No problems, not even a new leak.
"return expr" instances in generators (which latter may be generators
due to otherwise invisible "yield" stmts hiding in "if 0" blocks).
This was fun the first time, but this has gotten truly ugly now.
that required explicitly calling LazyList.clear() in the two tests that
use LazyList (I added a LazyList Fibonacci generator too).
A real bitch: the extremely inefficient first version of the 2-3-5 test
*looked* like a slow leak on Win98SE, but it wasn't "really": it generated
so many results that the heap grew over 4Mb (tons of frames! the number
of frames grows exponentially in that test). Then Win98SE malloc() starts
fragmenting address space allocating more and more heaps, and the visible
memory use grew very slowly while the disk was thrashing like mad.
Printing fewer results (i.e., keeping the heap burden under 4Mb) made
that illusion vanish.
Looks like there's no hope for plugging the LazyList leaks automatically
short of adding frameobjects and genobjects to gc. OTOH, they're very
easy to break by hand, and they're the only *kind* of plausibly realistic
leaks I've been able to provoke.
Dilemma.
Good news: Some of this stuff is pretty sophisticated (read nuts), and
I haven't bumped into a bug yet.
Bad news: If I run the doctest in an infinite loop, memory is clearly
leaking.
Guido van Rossum
Tim Peters
Neil Schemenauer
unknown