[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-10 Thread Benjamin Peterson 

Benjamin Peterson benja...@python.org added the comment:

I look at it this way: If I was browsing the 2.7 code and saw that type check, 
would I remove it in the bugfix release? No.

I'm going to mark this resolved. Thanks everyone.

--
resolution:  - works for me
status: open - closed

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-09 Thread Barry A. Warsaw 

Barry A. Warsaw ba...@python.org added the comment:

Raymond, I like your patch and I think it addresses the issue nicely.  I made 
one small change, which is to add a test for non-list-sequenceness instead of 
changing the existing __dir__is_list test.  I think both tests are useful to 
keep.

Benjamin, what do you think about this for 2.7.2?

--
Added file: http://bugs.python.org/file22302/12248.diff

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-09 Thread Benjamin Peterson 

Benjamin Peterson benja...@python.org added the comment:

2011/6/9 Barry A. Warsaw rep...@bugs.python.org:

 Barry A. Warsaw ba...@python.org added the comment:

 Raymond, I like your patch and I think it addresses the issue nicely.  I made 
 one small change, which is to add a test for non-list-sequenceness instead of 
 changing the existing __dir__is_list test.  I think both tests are useful to 
 keep.

 Benjamin, what do you think about this for 2.7.2?

My preference is to leave 2.7 alone (actually all maintenance
releases) and apply the patch to 3.3. It seems to me the type
restricts are tangentially only related to the issue. There's no need
to change the behavior for new-style classes, too.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-09 Thread Raymond Hettinger 

Raymond Hettinger raymond.hettin...@gmail.com added the comment:

My preference is to remove the type check.  It hasn't and won't serve a useful 
purpose so there's no reason to freeze it into the API and have it live on.

That being said, it probably doesn't matter one bit how this report gets 
resolved.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-04 Thread Barry A. Warsaw 

Barry A. Warsaw ba...@python.org added the comment:

Using sorted() makes sense to me.  

Note that I've at least accomplished one goal, which is to have a tracker issue 
that discusses the merits of the change.  That way, no matter what the RM 
decides, I can at least point to an issue for justification when I resolve the 
downstream bug. :)

Thanks!

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-04 Thread Raymond Hettinger 

Changes by Raymond Hettinger raymond.hettin...@gmail.com:


--
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Added file: http://bugs.python.org/file22246/dir.patch

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-04 Thread Soren Hansen 

Soren Hansen so...@linux2go.dk added the comment:

When I first investigated this problem (I reported the original bug on 
Launchpad), my first attempt to address this issue in pymox had me quite 
stumped. The class in question has a __getattr__ method. Up until now, this 
hasn't affected the use of dir(), but it does now. I really just wanted it 
return whatever it used to return (since that has worked so far), but realising 
that this was an old-style class, I couldn't just call super(TheClass, 
self).__dir__().

So my question is: If this change stays (which seems clear given that the only 
changes proposed here are ways of relaxing the type requirement of the __dir__ 
method's return value, not reverting the change altogether), and I have an 
old-style class with a __getattr__ defined, how do I make that class return 
whatever it would have usually returned for __dir__()?

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-04 Thread Benjamin Peterson 

Benjamin Peterson benja...@python.org added the comment:

2011/6/4 Soren Hansen rep...@bugs.python.org:

 Soren Hansen so...@linux2go.dk added the comment:

 When I first investigated this problem (I reported the original bug on 
 Launchpad), my first attempt to address this issue in pymox had me quite 
 stumped. The class in question has a __getattr__ method. Up until now, this 
 hasn't affected the use of dir(), but it does now. I really just wanted it 
 return whatever it used to return (since that has worked so far), but 
 realising that this was an old-style class, I couldn't just call 
 super(TheClass, self).__dir__().

 So my question is: If this change stays (which seems clear given that the 
 only changes proposed here are ways of relaxing the type requirement of the 
 __dir__ method's return value, not reverting the change altogether), and I 
 have an old-style class with a __getattr__ defined, how do I make that class 
 return whatever it would have usually returned for __dir__()?

Yes, this is a limitation of magic methods on old style classes. The
usual method is something like this:

def __getattr__(self, name):
if name == __dir__:
return self.__dir__
# Other stuff

Of course, the best fix is to use new-style classes. :)

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-04 Thread Soren Hansen 

Soren Hansen so...@linux2go.dk added the comment:

2011/6/4 Benjamin Peterson rep...@bugs.python.org:
 2011/6/4 Soren Hansen rep...@bugs.python.org:
 So my question is: If this change stays (which seems clear given that the 
 only changes proposed here are ways of relaxing the type requirement of the 
 __dir__ method's return value, not reverting the change altogether), and I 
 have an old-style class with a __getattr__ defined, how do I make that class 
 return whatever it would have usually returned for __dir__()?

 Yes, this is a limitation of magic methods on old style classes. The
 usual method is something like this:

    def __getattr__(self, name):
        if name == __dir__:
            return self.__dir__
        # Other stuff

 Of course, the best fix is to use new-style classes. :)

If I do this:

= test.py ==
class Foo:
def __getattr__(self, name):
if name == '__dir__':
return self.__dir__
return 'something else'

a = Foo()
print dir(a)


After a lot of this:
  File test.py, line 4, in __getattr__
return self.__dir__
  File test.py, line 4, in __getattr__
return self.__dir__
  File test.py, line 4, in __getattr__
return self.__dir__

...I end up with a RuntimeError: maximum recursion depth exceeded. I
can't say I'm surprised :)

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-04 Thread Benjamin Peterson 

Benjamin Peterson benja...@python.org added the comment:

2011/6/4 Soren Hansen rep...@bugs.python.org:

 Soren Hansen so...@linux2go.dk added the comment:

 2011/6/4 Benjamin Peterson rep...@bugs.python.org:
 2011/6/4 Soren Hansen rep...@bugs.python.org:
 So my question is: If this change stays (which seems clear given that the 
 only changes proposed here are ways of relaxing the type requirement of the 
 __dir__ method's return value, not reverting the change altogether), and I 
 have an old-style class with a __getattr__ defined, how do I make that 
 class return whatever it would have usually returned for __dir__()?

 Yes, this is a limitation of magic methods on old style classes. The
 usual method is something like this:

    def __getattr__(self, name):
        if name == __dir__:
            return self.__dir__
        # Other stuff

 Of course, the best fix is to use new-style classes. :)

 If I do this:

 = test.py ==
 class Foo:
    def __getattr__(self, name):
        if name == '__dir__':
            return self.__dir__
        return 'something else'

 a = Foo()
 print dir(a)
 

 After a lot of this:
  File test.py, line 4, in __getattr__
    return self.__dir__
  File test.py, line 4, in __getattr__
    return self.__dir__
  File test.py, line 4, in __getattr__
    return self.__dir__

 ...I end up with a RuntimeError: maximum recursion depth exceeded. I
 can't say I'm surprised :)

Ah, sorry I should have thought before writing that. :)
self.__class__.__dir__.__get__(self, self.__class__) should work,
though.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-04 Thread Soren Hansen 

Soren Hansen so...@linux2go.dk added the comment:

2011/6/5 Benjamin Peterson rep...@bugs.python.org:
 2011/6/4 Soren Hansen rep...@bugs.python.org:
 ...I end up with a RuntimeError: maximum recursion depth exceeded. I
 can't say I'm surprised :)
 Ah, sorry I should have thought before writing that. :)
 self.__class__.__dir__.__get__(self, self.__class__) should work,
 though.

Yeah, that one does seem to work. Excellent, thanks!

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Éric Araujo 

Changes by Éric Araujo mer...@netwok.org:


--
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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Jesús Cea Avión 

Changes by Jesús Cea Avión j...@jcea.es:


--
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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Benjamin Peterson 

Benjamin Peterson benja...@python.org added the comment:

No additional type-checking was added. The problem is that __dir__ didn't work 
on old-style classes at all in 2.7.1:

$ python
Python 2.7.1 (r271:86832, Mar 24 2011, 22:44:47)
[GCC 4.4.5] on linux2
Type help, copyright, credits or license for more information.
 class Foo:
... def __dir__(self):
... return ['a', 'b', 'c']
...
 class Bar:
... def __dir__(self):
... return ('a', 'b', 'c')
...
 print dir(Foo())
['__dir__', '__doc__', '__module__']
 print dir(Bar())
['__dir__', '__doc__', '__module__']

Loosening type-checks on dir() is fine with me but is really a 3.3 issue.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Arfrever Frehtes Taifersar Arahesis 

Changes by Arfrever Frehtes Taifersar Arahesis arfrever@gmail.com:


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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Nick Coghlan 

Nick Coghlan ncogh...@gmail.com added the comment:

Ah, I wondered about that when I saw Barry was using old-style classes in his 
example. Perhaps the answer then is to add a PyInstance_Check() to skip 
invocation of __dir__() completely for old-style classes?

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Benjamin Peterson 

Benjamin Peterson benja...@python.org added the comment:

2011/6/3 Nick Coghlan rep...@bugs.python.org:

 Nick Coghlan ncogh...@gmail.com added the comment:

 Ah, I wondered about that when I saw Barry was using old-style classes in his 
 example. Perhaps the answer then is to add a PyInstance_Check() to skip 
 invocation of __dir__() completely for old-style classes?

Uh, well, part of point of my checkin was to fix old style class
__dir__(). I think this is a bug in the package we're just exposing.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread R. David Murray 

R. David Murray rdmur...@bitdance.com added the comment:

I would guess that if you instead skipped __dir__ completely for old style 
classes it would expose a different bug in this or some other package.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Nick Coghlan 

Nick Coghlan ncogh...@gmail.com added the comment:

It would be broken in the same way that it was broken in 2.7.1 though. That can 
be a plus when it comes to maintenance releases.

OTOH, this does turn a silent failure (__dir__() ignored on old-style classes) 
into a noisy failure (must return a list).

If you make Barry's classes new-style, they break in 2.7.1 as well, so I'm 
coming around to a point of view that this is a legitimate fix that reveals a 
real bug in third party code (i.e. anyone that hits this had a __dir__ that 
previously wasn't getting invoked)

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Raymond Hettinger 

Raymond Hettinger raymond.hettin...@gmail.com added the comment:

I believe the type check was gratuitous to begin with and should be removed.  
There's no reason the result has to be a list.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Benjamin Peterson 

Benjamin Peterson benja...@python.org added the comment:

2011/6/3 Raymond Hettinger rep...@bugs.python.org:

 Raymond Hettinger raymond.hettin...@gmail.com added the comment:

 I believe the type check was gratuitous to begin with and should be removed.  
 There's no reason the result has to be a list.

The reason for it is that the sort() method is called on it.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Raymond Hettinger 

Raymond Hettinger raymond.hettin...@gmail.com added the comment:

Can sorted() be used instead?

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-03 Thread Raymond Hettinger 

Raymond Hettinger raymond.hettin...@gmail.com added the comment:

or something like:

   result = obj.__dir__()
   if not isinstance(result, list):
   result = list(result)
   result.sort()
   return result

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-02 Thread Barry A. Warsaw 

New submission from Barry A. Warsaw ba...@python.org:

I'm making this a release blocker for 2.7.2 because I want to ensure that the 
change is deliberate and appropriate.  This is triggered by a bug report in 
Ubuntu where the change in behavior was noticed:

https://bugs.launchpad.net/nova/+bug/791221/+index

I have two problems with the change that I'd like to describe.  First is the 
NEWS file entry:

- Correct lookup of __dir__ on objects. Among other things, this causes errors
  besides AttributeError found on lookup to be propagated.

This isn't associated with a tracker issue, so it's hard to know why this 
change was made, or whether there was any discussion of its impact.

Second, is this change appropriate for a maintenance release?  What problem 
does it fix and is that worth breaking existing packages for it?

I'll attach a simple test program.  Run this under 2.7.1 and it works, run it 
under 2.7.2rc1 and you get a TypeError.

--
assignee: benjamin.peterson
components: Interpreter Core
files: foo.py
messages: 137500
nosy: barry, benjamin.peterson
priority: release blocker
severity: normal
status: open
title: __dir__ semantics changed in Python 2.7.2
type: behavior
versions: Python 2.7
Added file: http://bugs.python.org/file5/foo.py

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-02 Thread R. David Murray 

R. David Murray rdmur...@bitdance.com added the comment:

As I recall the issue that triggered the change was reported by Michael Foord, 
so I'm adding him as nosy too.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-02 Thread Nick Coghlan 

Nick Coghlan ncogh...@gmail.com added the comment:

Hmm, that behaviour looks unrelated to the specific problem Michael reported.

The initial problem in this space was that defining __dir__() completely 
determined the result of dir() calls, but object.__dir__() didn't actually 
work, so you couldn't easily get the standard list of attributes in order to 
supplement it.

I don't believe there is any reason to have tightened up the type constraints 
while fixing that - dir() should be returning sorted(obj.__dir__()) and not 
caring about the exact return type of the magic method.

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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-02 Thread Andreas Stührk 

Changes by Andreas Stührk andy-pyt...@hammerhartes.de:


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[issue12248] __dir__ semantics changed in Python 2.7.2

2011-06-02 Thread Raymond Hettinger 

Raymond Hettinger raymond.hettin...@gmail.com added the comment:

 I don't believe there is any reason to have tightened up
 the type constraints while fixing that - dir() should be
 returning sorted(obj.__dir__()) and not caring about the 
 exact return type of the magic method.

+1

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