[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Ben North <b...@redfrontdoor.org> added the comment:

Terry in msg310785:
> As I expected from the fact that Ben once did a separate 2.7
> version, the auto backport for 2.7 failed.  Ben, since you know what
> code changes are needed, can you prepare a backport (cherry pick)
> PR?

Yes, that's right, there were some differences between the approaches
in Py2 and Py3.  I've created PR5357 for the 2.7 backport.

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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Change by Ben North <b...@redfrontdoor.org>:


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pull_requests: +5203
stage: needs patch -> patch review

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[issue32137] Stack overflow in repr of deeply nested dicts

[Ben North]

Change by Ben North <b...@redfrontdoor.org>:


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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Ben North <b...@redfrontdoor.org> added the comment:

PR4823 created as per msg308086.

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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Ben North added the comment:

Is anything further needed from me before this can be reviewed?

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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Changes by Ben North b...@redfrontdoor.org:


Added file: http://bugs.python.org/file31089/against-9bf89c909bd4-3.3-1.patch

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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Ben North added the comment:

I'll attach fresh patches, one against latest 2.7 and one against
latest 3.3 (unchanged apart from headers from previous patch).

Both branches pass

./python -m test.regrtest -R20:30 test_dictviews

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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Changes by Ben North b...@redfrontdoor.org:


Added file: http://bugs.python.org/file31088/against-6e1dd1ce95b8-2.7-1.patch

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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Ben North added the comment:

New patch, fixing nit noted in msg193624:

non-error-recursive-dictview-3.3-1.patch

Otherwise same as previous

non-error-recursive-dictview-3.3.patch

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Added file: 
http://bugs.python.org/file31025/non-error-recursive-dictview-3.3-1.patch

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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

Ben North added the comment:

New patch including tests attached, against 3.3.  Terry Reedy's example
above now gives

 d = {}
 d[1] = d.keys()
 d[2] = d.values()
 d
{1: dict_keys([1, 2]), 2: dict_values([dict_keys([1, 2]), ...])}

which I think is preferable.

Summary of patch:

dictobject.c:

dictview_repr() now uses a Py_ReprEnter() / Py_ReprLeave() pair to
check for recursion, and produces ... if so.  I think I've got the
behaviour correct in the case that PySequence_List() fails, but
couldn't find a way to trigger this in testing.

test_dictviews.py:

test_recursive_repr() checks for the correct string (containing
...) rather than a RuntimeError.

test_deeply_nested_repr() is a new function, aiming to replace the
original test_recursive_repr().  It checks that a RuntimeError is
raised in the case of a non-recursive but deeply nested structure.

Under --with-pydebug,

./python -m test.regrtest -R20:30 test_dictviews

passes.

--
Added file: 
http://bugs.python.org/file31022/non-error-recursive-dictview-3.3.patch

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[issue18533] Avoid error from repr() of recursive dictview

[Ben North]

New submission from Ben North:

#18019 noted the following crash in earlier 2.7:

 d={}
 d[42]=d.viewvalues()
 d
segmentation fault

This issue has been fixed; the behaviour now is that a RuntimeError is
produced for a recursive dictionary view:

 d={}
 d[42]=d.viewvalues()
 d # (output line-broken:)
{42: Traceback (most recent call last):
  File stdin, line 1, in module
RuntimeError: maximum recursion depth exceeded
  while getting the repr of a list

Before finding this, though, I'd investigated and made a patch which
produces a similar ... output to a recursive dictionary.  Reworking
against current 2.7, the behaviour would be:

 x={}
 x[42]=x
 x # existing behaviour for dictionaries:
{42: {...}}

 d={}
 d[42]=d.viewvalues()
 d # new behaviour:
{42: dict_values([...])}
 d[43]=d.viewitems()
 d # (output line-broken:)
{42: dict_values([..., dict_items([(42, ...), (43, ...)])]),
 43: dict_items([(42, dict_values([..., ...])), (43, ...)])}

Attached is the patch, against current 2.7 branch.  If there is interest
in applying this, I will create a proper patch (changelog entry, fix to
Lib/test/test_dictviews.py, etc.).

On python-dev, Gregory Smith noted:

Given that the RuntimeError fix has been released, your proposed
... behavior is arguably a new feature so I'd only expect this to
make sense for consideration in 3.4, not 2.7.  (if accepted at all)

[http://mail.python.org/pipermail/python-dev/2013-July/127489.html]

so I have marked for consideration for versions 2.7 and 3.4.

--
components: Interpreter Core
files: non-error-recursive-dictview.patch
keywords: patch
messages: 193570
nosy: bennorth
priority: normal
severity: normal
status: open
title: Avoid error from repr() of recursive dictview
type: behavior
versions: Python 2.7, Python 3.4
Added file: http://bugs.python.org/file31019/non-error-recursive-dictview.patch

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[issue5821] Documentation: mention 'close' and iteration for tarfile.TarFile.extractfile()

[Ben North]

New submission from Ben North benno...@users.sourceforge.net:

The current documentation for tarfile.TarFile.extractfile() does not
mention that the returned 'file-like object' supports close() and also
iteration.  The attached patch (against svn trunk) fixes this.

(Background: I was wondering whether I could write

  def process_and_close_file(f_in):
  with closing(f_in) as f:
  # Do stuff with f.

and have it work whether f_in was a true file or the return value of
extractfile(), and thought from the documentation that I couldn't.  Of
course, I could have just tried it, but I think fixing the documentation
wouldn't hurt.)

--
assignee: georg.brandl
components: Documentation
files: tarfile.rst.patch
keywords: patch
messages: 86366
nosy: bennorth, georg.brandl
severity: normal
status: open
title: Documentation: mention 'close' and iteration for 
tarfile.TarFile.extractfile()
type: feature request
Added file: http://bugs.python.org/file13749/tarfile.rst.patch

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[issue5191] Partial function application 'from the right'

[Ben North]

New submission from Ben North benno...@users.sourceforge.net:

The functools module includes a 'partial' class, which allows partial
function application either by positional arguments or keyword
arguments.  However, it cannot be used to create, for example, a
function splitting a string on commas, or a function to extracts logs to
base 10.  I posted

   http://mail.python.org/pipermail/python-dev/2009-January/085638.html

which suggested a 'partial_right' feature, such that the following would
work:

import functools, math

split_comma = functools.partial_right(str.split, ',')
split_comma('a,b,c')
   ['a', 'b', 'c']

log_10 = functools.partial_right(math.log, 10.0)
log_10(100.0)
   2.0

There was some useful discussion, but generally the feeling was that the
extra complexity outweighed the potential benefits.  Also, chained
partial applications were troublesome.

The overlap in functionality between 'partial_right' and an existing
patch (#1706256) to allow skipping of positional arguments was raised.

I think the present issue should probably be closed/rejected, but it was
suggested on the mailing list that having the issue and patch on the
record might be useful.  Patches are against 2.6.1 source.

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nosy: bennorth
severity: normal
status: open
title: Partial function application 'from the right'
type: feature request

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[issue5191] Partial function application 'from the right'

[Ben North]

Changes by Ben North benno...@users.sourceforge.net:


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keywords: +patch
Added file: http://bugs.python.org/file12991/_functoolsmodule.patch

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[issue5191] Partial function application 'from the right'

[Ben North]

Changes by Ben North benno...@users.sourceforge.net:


Added file: http://bugs.python.org/file12992/test_functools.patch

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