Gareth Rees added the comment:
This kind of question is frequently asked (#3128, #29977, #28690, #30973,
#1737127, etc.), and so maybe it deserves an answer somewhere in the Python
documentation.
--
resolution: -> wont fix
stage: -> resolved
status: open -&g
Gareth Rees added the comment:
The way to avoid this behaviour is to disallow the attempts at matching that
you know are going to fail. As Serhiy described above, if the search fails
starting at the first character of the string, it will move forward and try
again starting at the second
Gareth Rees added the comment:
I also have a use case that would benefit from nanosecond resolution in
Python's datetime objects, that is, representing and querying the results of
clock_gettime() in a program trace.
On modern Linuxes with a vDSO, clock_gettime() does not require a system
Gareth Rees added the comment:
Tagging vstinner as you have touched Modules/signalmodule.c a few times in the
last year. What do you think?
--
nosy: +vstinner
___
Python tracker
<https://bugs.python.org/issue45
Change by Gareth Rees :
--
keywords: +patch
pull_requests: +27529
stage: -> patch review
pull_request: https://github.com/python/cpython/pull/29266
___
Python tracker
<https://bugs.python.org/issu
New submission from Gareth Rees :
BACKGROUND
On Linux, "man 7 signal" includes SIGSTKFLT in its table of "various other
signals":
Signal Value Action Comment
───
SIGSTKFLT -,16,-
Gareth Rees added the comment:
If the problem is accidental use of the result of PyFloat_AS_DOUBLE() as an
lvalue, why not use the comma operator to ensure that the result is an rvalue?
The C99 standard says "A comma operator does not yield an lvalue" in §6.5.17; I
imagine there
Gareth Rees added the comment:
The proposed change adds a Boolean flag to os.path.getsize() so that it returns:
os.stat(filename).st_blocks * 512
(where the 512 is the file system block size on Linux; some work is needed to
make this portable to other operating systems).
The Boolean
Gareth Rees added the comment:
Is there anything I can do to move this forward?
--
___
Python tracker
<https://bugs.python.org/issue40707>
___
___
Python-bug
Gareth Rees added the comment:
The following test cases in test_subprocess.py call the communicate() method
and then immediately assert that returncode attribute has the expected value:
* test_stdout_none
* test_stderr_redirect_with_no_stdout_redirect
* test_stdout_filedes_of_stdout
Change by Gareth Rees :
--
keywords: +patch
pull_requests: +19559
stage: -> patch review
pull_request: https://github.com/python/cpython/pull/20283
___
Python tracker
<https://bugs.python.org/issu
New submission from Gareth Rees :
When using subprocess.Popen.communicate(), it is natural to wonder how to get
the exit code of the subprocess. However, the documentation [1] says:
Interact with process: Send data to stdin. Read data from stdout and
stderr, until end-of-file
Gareth Rees added the comment:
I'd like to push back on the idea that graphs with isolated vertices are
"unusual cases" as suggested by Raymond.
A very common use case (possibly the most common) for topological sorting is
job scheduling. In this use case you have a collection of
Gareth Rees added the comment:
Just to elaborate on what I mean by "bug magnet". (I'm sure Pablo understands
this, but there may be other readers who would like to see it spelled out.)
Suppose that you have a directed graph represented as a mapping from a vertex
to an iterable
Gareth Rees added the comment:
I approve in general with the principle of including a topological sort
algorithm in the standard library. However, I have three problems with the
approach in PR 11583:
1. The name "topsort" is most naturally parsed as "top sort" which coul
Gareth Rees <g...@garethrees.org> added the comment:
The behaviour of the * operator (and the associated gotcha) is documented under
"Common sequence operations" [1]:
Note that items in the sequence s are not copied; they are referenced
multiple times. This often h
Gareth Rees <g...@garethrees.org> added the comment:
convertdate does not document which version of the Islamic calendar it uses,
but looking at the source code, it seems that it uses a rule-based calendar
which has a 30-year cycle with 11 leap years. This won't help Haneef, who wants
t
Gareth Rees <g...@garethrees.org> added the comment:
It is a substantial undertaking, requiring a great deal of expertise, to
implement the Islamic calendar. The difficulty is that there are multiple
versions of the calendar. In some places the calendar is based on human
obser
Gareth Rees <g...@garethrees.org> added the comment:
You're welcome.
--
___
Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue28647>
___
Gareth Rees added the comment:
I've made a pull request. (Not because I expect it to be merged as-is, but to
provide a starting point for discussion.)
--
nosy: +petri.lehtinen, vinay.sajip
___
Python tracker <rep...@bugs.python.org>
Changes by Gareth Rees <g...@garethrees.org>:
--
pull_requests: +2849
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue24869>
___
_
Gareth Rees added the comment:
This is a race condition — when os.kill returns, that means that the signal has
been delivered, but it does not mean that the subprocess has exited yet. You
can see this by inserting a sleep after the kill and before the liveness check:
print(proc.is_alive
Gareth Rees added the comment:
This is the usual exponential backtracking behaviour of Python's regex engine.
The problem is that the regex
(?:[^*]+|\*[^/])*
can match against a string in exponentially many ways, and Python's regex
engine tries all of them before giving up
Changes by Gareth Rees <g...@garethrees.org>:
--
pull_requests: +2801
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue19896>
___
_
Gareth Rees added the comment:
(If he hasn't, I don't think I can make a PR because I read his patch and so
any implementation I make now is based on his patch and so potentially
infringes his copyright.)
--
___
Python tracker <
Gareth Rees added the comment:
Has Antony Lee has made a copyright assignment?
--
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/i
Changes by Gareth Rees <g...@garethrees.org>:
--
nosy: +benjamin.peterson
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue19896>
___
Gareth Rees added the comment:
This was already noted in issue29714 and fixed by Xiang Zhang in commit
b76ad5121e2.
--
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/i
Gareth Rees added the comment:
Test case minimization:
Python 3.6.1 (default, Apr 24 2017, 06:18:27)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more informa
Gareth Rees added the comment:
Patch looks good to me. The test cases are not very systematic (why only int,
double, and long long?), but that's not the fault of the patch and shouldn't
prevent its being applied.
--
nosy: +g...@garethrees.org
Gareth Rees added the comment:
I propose:
1. Ask Richard Oudkerk why in changeset 3b82e0d83bf9 the temporary file is
zero-filled and not truncated. Perhaps there's some file system where this is
necessary? (I tested HFS+ which doesn't support sparse files, and zero-filling
seems
Gareth Rees added the comment:
I see now that the default start method is 'fork' (except on Windows), so
calling set_start_method is unnecessary.
Note that you don't have to edit multiprocessing/heap.py, you can
"monkey-patch" it in the program that needs the anonymous mapping:
Gareth Rees added the comment:
Nonetheless this is bound to be a nasty performance for many people doing big
data processing with NumPy/SciPy/Pandas and multiprocessing and moving from 2
to 3, so even if it can't be fixed, the documentation ought to warn about the
problem and explain how
Gareth Rees added the comment:
If you need the 2.7 behaviour (anonymous mappings) in 3.5 then you can still do
it, with some effort. I think the approach that requires the smallest amount of
work would be to ensure that subprocesses are started using fork(), by calling
Gareth Rees added the comment:
Note that some filesystems (e.g. HFS+) don't support sparse files, so creating
a large Arena will still be slow on these filesystems even if the file is
created using ftruncate().
(This could be fixed, for the "fork" start method only, by using anon
Gareth Rees added the comment:
In Python 2.7, multiprocessing.heap.Arena uses an anonymous memory mapping on
Unix. Anonymous memory mappings can be shared between processes but only via
fork().
But Python 3 supports other ways of starting subprocesses (see issue 8713 [1])
and so an anonymous
Gareth Rees added the comment:
RFC 4648 section 3.5 says:
The padding step in base 64 and base 32 encoding can, if improperly
implemented, lead to non-significant alterations of the encoded data.
For example, if the input is only one octet for a base 64 encoding,
then all six bits
Gareth Rees added the comment:
See also issue28690, issue212521, issue753711, issue1515829, etc.
--
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/i
Gareth Rees added the comment:
The problem here is that both "." and "\s" match a whitespace character, and
because you have the re.DOTALL flag turned on this includes "\n", and so the
number of different ways in which (.|\s)* can be matched against a string
Gareth Rees added the comment:
Thank you, Mark (and everyone else who helped).
--
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/i
Gareth Rees added the comment:
Thanks for the revised patch, Mark. The new tests look good.
--
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/i
Gareth Rees added the comment:
Here's a patch that implements my proposal (1) -- under this patch, tokens read
from an input stream belong to a subtype of str with startline and endline
attributes giving the line numbers of the first and last character of the
token. This allows the accurate
Gareth Rees added the comment:
In Windows, under cmd.exe, you can use %errorlevel%
--
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/i
Gareth Rees added the comment:
Is there any chance of making progress on this issue? Is there anything wrong
with my patch? Did I omit any relevant point in my message of 2016-06-11 16:26?
It would be nice if this were not left in limbo for another four years
Gareth Rees added the comment:
In order for this to work, the __getitem__ method needs to be:
def __getitem__(self, key):
if 0 <= key < self.n:
return self.elem
else:
raise IndexError(key)
But unfortunately this is very bad for the perfo
Gareth Rees added the comment:
Couldn't the test case use something like this to avoid allocating so much
memory?
from collections.abc import Sequence
class RepeatedSequence(Sequence):
"""Immutable sequence of n repeats of elem."""
Gareth Rees added the comment:
This is a well-known gotcha with backtracking regexp implementations. The
problem is that in the alternation "( +|'[^']*'|\"[^\"]*\"|[^>]+)" there are
some characters (space, apostrophe, double quotes) that match multiple
alter
New submission from Gareth Rees:
On macOS Sierra (OSX 10.12.1):
$ ./configure --with-pydebug && make
[... lots of output omitted ...]
gcc -c -Wno-unused-result -Wsign-compare -g -O0 -Wall -Wstrict-prototypes
-std=c99 -Wextra -Wno-unused-result -Wno-unused-parameter
-Wno
Gareth Rees added the comment:
Here's a patch that copies the text for the -u option from the man page to the
--help output.
--
keywords: +patch
Added file: http://bugs.python.org/file45463/issue28647.patch
___
Python tracker <rep...@bugs.python.
Gareth Rees added the comment:
The output of "python3.5 --help" says:
-u : unbuffered binary stdout and stderr, stdin always buffered;
also PYTHONUNBUFFERED=x
see man page for details on internal buffering relating to '-u'
If you look at the man page as
New submission from Gareth Rees:
The type objects constructed by the metaclasses in the typing module are
hashable and comparable for equality:
>>> from typing import *
>>> {Mapping[str, int], Mapping[int, str]}
{typing.Mapping[int, str], typing.Mapping[str, int]}
Gareth Rees added the comment:
A third alternative:
3. Add a method whose effect is to consume comments and whitespace, but which
does not yield a token. You could then call this method, and then look at
shlex.lineno, which will be the line number of the first character of the next
token
Gareth Rees added the comment:
Just to restate the problem:
The use case is that when emitting an error message for a token, we want to
include the number of the line containing the token (or the number of the line
where the token started, if the token spans multiple lines, as it might
Gareth Rees added the comment:
Here's a patch improving the grammar in the tarfile documentation.
--
keywords: +patch
nosy: +Gareth.Rees
Added file: http://bugs.python.org/file43375/issue27306.patch
___
Python tracker <rep...@bugs.python.org>
Gareth Rees added the comment:
Thank you for applying this patch.
--
___
Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue20508>
___
___
Gareth Rees added the comment:
Let's not allow the perfect to be the enemy of the good here.
The issue I reported is a very specific one: in Python 2.7, if you pass a long
to sys.exit, then the value of the long is not used as the exit code. This is
bad because functions like os.spawnv
Gareth Rees added the comment:
I've attached a revised patch that addresses Berker Peksag's concerns:
1. The message associated with the IndexError is now "address out of range"
with no information about which address failed or why.
2. There's a new test case for an IndexError fr
Gareth Rees added the comment:
If you read the documentation for urllib.parse.urlencode [1], you'll
see that it says:
The value element in itself can be a sequence and in that case, if
the optional parameter doseq is evaluates to True, individual
key=value pairs separated
New submission from Gareth Rees:
The Expressions documentation contains the text:
* Sets and frozensets define comparison operators to mean subset and superset
tests. Those relations do not define total orderings (the two sets ``{1,2}``
and {2,3} are not equal, nor subsets of one another
Changes by Gareth Rees g...@garethrees.org:
--
title: Bulit-in Types documentation doesn't explain how dictionaries are
compared for equality - Built-in Types documentation doesn't explain how
dictionaries are compared for equality
___
Python
Gareth Rees added the comment:
The documentation says that weakref.Proxy objects are not hashable because
this avoids a number of problems related to their fundamentally mutable
nature, and prevent their use as dictionary keys.
Hashable objects must be immutable, otherwise the hash might
Gareth Rees added the comment:
I don't see any reason for proxy objects to be less hashable than ref objects.
The difference is that unlike a ref object, a proxy object is supposed to
forward its method calls to the proxied object. So consider what happens if you
forward the __hash__ method
Gareth Rees added the comment:
Hashable is particularly misleading, because weakref.Proxy objects are not
hashable regardless of the referent.
--
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue24067
Gareth Rees added the comment:
Not just Iterator, but Container, Hashable, Iterable, and Sized too!
import weakref
class C: pass
o = C()
w = weakref.proxy(o)
from collections.abc import *
isinstance(w, Container)
True
isinstance(w, Hashable)
True
Gareth Rees added the comment:
This is a duplicate of #22180, which was fixed in changeset 9c250f34bfa3 by
Raymond Hettinger in branch '3.4'. The fix just removes the bad example, as in
my patch. So I suggest that this issue be closed as a duplicate
Gareth Rees added the comment:
How did you get this warning?
This looks like runtime output from a program built using Clang/LLVM with
-fsanitize=undefined. See here:
http://clang.llvm.org/docs/UsersManual.html#controlling-code-generation
Signed integer overflow is undefined behaviour, so
Gareth Rees added the comment:
It would be better to accept a key function instead of a comparison
function (cf. heapq.nlargest and heapq.nsmallest).
But note that this has been proposed before and rejected: see
issue1904 where Raymond Hettinger provides this rationale:
Use cases aside
Gareth Rees added the comment:
The JSON implementation uses these tests to determine how to serialize a Python
object:
isinstance(o, (list, tuple))
isinstance(o, dict)
So any subclasses of list and tuple are serialized as a list, and any subclass
of dict is serialized as an object
Gareth Rees added the comment:
If 100 doesn't work for you, try a larger number.
--
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue20727
Gareth Rees added the comment:
I suspect I messed up the timing I did yesterday, because today I find that 100
isn't large enough, but here's what I found today (in Python 3.3):
from timeit import timeit
test = [tuple(range(300))] + [()] * 100
timeit(lambda:list(roundrobin1
Gareth Rees added the comment:
But now that I look at the code more carefully, the old recipe also has O(n^2)
behaviour, because cycle(islice(nexts, pending)) costs O(n) and is called O(n)
times. To have worst-case O(n) behaviour, you'd need something like this:
from collections import
Gareth Rees added the comment:
benchmarks show it to be more than twice as fast
I'm sure they do, but other benchmarks show it to be more than twice as slow.
Try something like:
iterables = [range(100)] + [()] * 100
--
nosy: +Gareth.Rees
Gareth Rees added the comment:
Thanks for your work on this, Terry. I apologise for the complexity of my
original report, and will try not to do it again.
--
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue12691
Gareth Rees added the comment:
Sorry about that; here it is. I had second thoughts about recommending zip() as
an alternative (that would only work for cases where the None was constant; in
other cases you might need lambda *args: args, but this seemed too
complicated), so the note now says
Gareth Rees added the comment:
The failing example is:
d = {}
keys = range(256)
vals = map(chr, keys)
map(operator.setitem, [d]*len(keys), keys, vals)
which works in Python 2 where map returns a list, but not in Python 3 where map
returns an iterator.
Doc/library
Changes by Gareth Rees g...@garethrees.org:
--
keywords: +patch
Added file: http://bugs.python.org/file34059/operator.patch
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue20606
Gareth Rees added the comment:
It's not a case of internal storage overflowing. The error is from
Modules/mathmodule.c:1426 and it's the input 10**19 that's too large
to convert to a C long. You get the same kind of error in other
places where PyLong_AsLong or PyLong_AsInt is called on a
user
Gareth Rees added the comment:
I did some research on the cause of this issue. The assertion was
added in this change by Jeremy Hylton in August 2006:
https://mail.python.org/pipermail/python-checkins/2006-August/055812.html
(The corresponding Mercurial commit is here:
http://hg.python.org
Changes by Gareth Rees g...@garethrees.org:
--
assignee: - docs@python
components: +Documentation, Tests
nosy: +docs@python
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue12691
Changes by Gareth Rees g...@garethrees.org:
Removed file: http://bugs.python.org/file33919/Issue12691.patch
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue12691
New submission from Gareth Rees:
If you pass an object of the wrong type to str.join, Python raises a
TypeError with no error message:
Python 3.4.0b3 (default, Jan 27 2014, 02:26:41)
[GCC 4.2.1 Compatible Apple LLVM 5.0 (clang-500.2.79)] on darwin
Type help, copyright, credits
New submission from Gareth Rees:
If you try to look up an out-of-range address from an object returned
by ipaddress.ip_network, then ipaddress._BaseNetwork.__getitem__
raises an IndexError with no message:
Python 3.4.0b3 (default, Jan 27 2014, 02:26:41)
[GCC 4.2.1 Compatible Apple LLVM
Changes by Gareth Rees g...@garethrees.org:
--
type: behavior - enhancement
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue20508
___
___
Python
Gareth Rees added the comment:
Here's a revised patch using Ezio's suggestion (Return the number of items of
a sequence or container).
--
Added file: http://bugs.python.org/file33904/len-set.patch
___
Python tracker rep...@bugs.python.org
http
Changes by Gareth Rees g...@garethrees.org:
--
title: Documentation for len() fails to mention that it works on sets -
Documentation for len() fails to mention that it works on sets
versions: +Python 3.4
___
Python tracker rep...@bugs.python.org
Gareth Rees added the comment:
Patch attached. I added a test case to Lib/test/test_sys.py.
--
Added file: http://bugs.python.org/file33906/exit.patch
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue14376
New submission from Gareth Rees:
Lib/test/test_sys.py contains test cases with incorrect comments -- or
comments with incorrect test cases, if you prefer:
# call without argument
try:
sys.exit(0)
except SystemExit as exc:
self.assertEqual(exc.code, 0
Gareth Rees added the comment:
What about a documentation change instead? The future_builtins chapter
http://docs.python.org/2/library/future_builtins.html in the
standard library documentation could note the incompatibility.
I've attached a patch which adds the following note
Gareth Rees added the comment:
I normally try not to make changes while we're in here for fear of
introducing errors! But I guess the test cases are less critical, so
I've taken your review comments as a license to submit a revised patch
that:
* incorporates your suggestion to use
Gareth Rees added the comment:
Here's a revised patch for Terry (Return the number of items of a sequence or
collection.)
--
Added file: http://bugs.python.org/file33916/len-set.patch
___
Python tracker rep...@bugs.python.org
http://bugs.python.org
Gareth Rees added the comment:
Yury, let me see if I can move this issue forward. I clearly haven't
done a good job of explaining these problems, how they are related,
and why it makes sense to solve them together, so let me have a go
now.
1. tokenize.untokenize() raises AssertionError if you
Changes by Gareth Rees g...@garethrees.org:
--
nosy: +benjamin.peterson
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue12691
___
___
Python-bugs
New submission from Gareth Rees:
The help text for the len() built-in function says:
Return the number of items of a sequence or mapping.
This omits to mention that len() works on sets too. I suggest this be changed
to:
Return the number of items of a sequence, mapping, or set
New submission from Gareth Rees:
In Python 2.7, future_builtins.map accepts None as its first (function)
argument:
Python 2.7.5 (default, Aug 1 2013, 01:01:17)
from future_builtins import map
list(map(None, range(3), 'ABC'))
[(0, 'A'), (1, 'B'), (2, 'C')]
But in Python 3.x
Gareth Rees added the comment:
I considered suggesting container, but the problem is that container is
used elsewhere to mean object supporting the 'in' operator (in particular,
collections.abc.Container has a __contains__ method but no __len__ method).
The abstract base class for object
Gareth Rees g...@garethrees.org added the comment:
Wouldn't you also have to deal with possible errors from the PyInt_AsLong
call?
Good point. But I note that Python 3 just does
exitcode = (int)PyLong_AsLong(value);
so maybe it's not important to do error handling here
New submission from Gareth Rees g...@garethrees.org:
The documentation for sys.exit says, The optional argument arg can be an
integer giving the exit status (defaulting to zero), or another type of object.
However, the arguments that are treated as exit statuses are actually subtypes
of int
Gareth Rees g...@garethrees.org added the comment:
After changing NULL to (int *)1, all tests pass.
--
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue12700
Gareth Rees g...@garethrees.org added the comment:
All tests now pass.
--
___
Python tracker rep...@bugs.python.org
http://bugs.python.org/issue12700
___
___
Python-bugs
Gareth Rees g...@garethrees.org added the comment:
I think I can make these changes independently and issue two patches, one
fixing the problems with untokenize listed here, and another improving tokenize.
I've just noticed a third bug in untokenize: in full mode, it doesn't handle
backslash
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