Re: [Python-Dev] chained assignment weirdity

On 08.11.12 03:11, Ned Batchelder wrote: > Sorry, I should have been clearer: I was asking about weird not to say, > "This is weird and should be changed!", but to get clarification from > Serhiy about his statement, " It will be weird if a dict comprehension > and a plain loop will be inconsist

Re: [Python-Dev] chained assignment weirdity

On 11/7/2012 5:11 PM, Terry Reedy wrote: On 11/7/2012 4:39 PM, Ned Batchelder wrote: Just to be clear: the reference guide says that the behavior *SHOULD BE* (but is not yet) this: Python 3.3.0 >>> {print("a"):print("b")} a b {None: None} >>> d = {} >>> d[print("

Re: [Python-Dev] chained assignment weirdity

On 08/11/12 08:39, Ned Batchelder wrote: Just to be clear: the reference guide says that the behavior *SHOULD BE* (but is not yet) this: Python 3.3.0 >> {print("a"):print("b")} a b {None: None} That was the behaviour of Python 2.4: py> def pr(x): ... print x ... py> {pr(1): pr(2), pr

Re: [Python-Dev] chained assignment weirdity

On 11/7/2012 4:39 PM, Ned Batchelder wrote: Just to be clear: the reference guide says that the behavior *SHOULD BE* (but is not yet) this: Python 3.3.0 >>> {print("a"):print("b")} a b {None: None} >>> d = {} >>> d[print("a")] = print("b") b a >>> Is

Re: [Python-Dev] chained assignment weirdity

The dict display is considered an *expression* and thus must follow the L2R rule. The assignment is explicitly covered by the R2L rule for assignments (only). Weird or not, those are the rules, and I don't want to change them. On Wed, Nov 7, 2012 at 1:39 PM, Ned Batchelder wrote: > > On 11/7/2012

Re: [Python-Dev] chained assignment weirdity

On 11/7/2012 12:08 PM, Serhiy Storchaka wrote: On 07.11.12 17:12, Nick Coghlan wrote: Since you've indicated the implementation is in the wrong here and you also want to preserve opcode semantics, I think Skip's patch is correct, but also needs to be applied to dict comprehensions (now we have

Re: [Python-Dev] chained assignment weirdity

On 11/7/2012 10:17 AM, Guido van Rossum wrote: Ok, somebody go for it! (Also please refer to my pronouncement in the bug -- I've gotta run.) Done. http://bugs.python.org/issue11205?@ok_message=msg 175120 -- Terry Jan Reedy ___ Python-Dev mailing lis

Re: [Python-Dev] chained assignment weirdity

On 11/7/2012 9:54 AM, Guido van Rossum wrote: Hm. I really don't think that is a good development for Python to compromise in the area of expression evaluation order where side effects are involved. I agreee. I think Python's simple left to right evaluation order is one of its virtues. A g

Re: [Python-Dev] chained assignment weirdity

On 07.11.12 17:12, Nick Coghlan wrote: Since you've indicated the implementation is in the wrong here and you also want to preserve opcode semantics, I think Skip's patch is correct, but also needs to be applied to dict comprehensions (now we have them). The extra bytecode is only ROT_TWO, which

Re: [Python-Dev] chained assignment weirdity

Ok, somebody go for it! (Also please refer to my pronouncement in the bug -- I've gotta run.) On Wed, Nov 7, 2012 at 7:12 AM, Nick Coghlan wrote: > On Thu, Nov 8, 2012 at 12:54 AM, Guido van Rossum > wrote: > > On Wed, Nov 7, 2012 at 4:13 AM, Ned Batchelder > wrote: > >> If the bug report is

Re: [Python-Dev] chained assignment weirdity

On Thu, Nov 8, 2012 at 12:54 AM, Guido van Rossum wrote: > On Wed, Nov 7, 2012 at 4:13 AM, Ned Batchelder wrote: >> If the bug report is accurate, CPython and the reference manual have >> disagreed since Python 2.5, and many of us are now surprised to hear it, >> which means there can't have been

Re: [Python-Dev] chained assignment weirdity

On Thu, Nov 8, 2012 at 1:54 AM, Guido van Rossum wrote: > On Wed, Nov 7, 2012 at 4:13 AM, Ned Batchelder wrote: >> We've gone out of our way to >> maintain backward compatibility with the implemented behavior before >> (ordering of dict keys, for example). > > Not sure what you're referencing her

Re: [Python-Dev] chained assignment weirdity

On Wed, Nov 7, 2012 at 4:13 AM, Ned Batchelder wrote: > I think it's unfortunate that the current patch in the referenced bug ( > http://bugs.python.org/issue11205 ) fixes the "problem" by adding one more > bytecode to the compiled Python. The other alternative seems to be changing > the meaning

Re: [Python-Dev] chained assignment weirdity

On 7 November 2012 15:16, Chris Angelico wrote: > On Thu, Nov 8, 2012 at 1:11 AM, Nick Coghlan wrote: >> "The implementation is right, the docs are wrong" sounds good to me, >> as it's easy to justify the out of order evaluation in terms of the >> equivalent item assignment statements: > > What d

Re: [Python-Dev] chained assignment weirdity

On Thu, Nov 8, 2012 at 1:11 AM, Nick Coghlan wrote: > "The implementation is right, the docs are wrong" sounds good to me, > as it's easy to justify the out of order evaluation in terms of the > equivalent item assignment statements: What do other Pythons than CPython do currently? Or is it "The

Re: [Python-Dev] chained assignment weirdity

On Wed, Nov 7, 2012 at 10:13 PM, Ned Batchelder wrote: > There are plenty of places where different Python implementations differ, > and even careful observers had different ideas about how keys and values > were ordered in dict displays ("I thought it was like a function call," vs, > "I thought

Re: [Python-Dev] chained assignment weirdity

On 11/6/2012 5:12 PM, Guido van Rossum wrote: On Tue, Nov 6, 2012 at 9:58 AM, Ned Batchelder wrote: On 11/6/2012 11:26 AM, R. David Murray wrote: On Tue, 06 Nov 2012 18:14:38 +0200, Serhiy Storchaka wrote: Another counterintuitive (and possible wrong) example: >>> {print('foo'): print

Re: [Python-Dev] chained assignment weirdity

On 06.11.12 21:00, Ned Batchelder wrote: If someone really needs to control whether the keys or values are evaluated first, they shouldn't use a dict literal. Not only a dict literal. >>> {print('foo'): print('bar') for x in [1]} bar foo {None: None} _

Re: [Python-Dev] chained assignment weirdity

On Tue, Nov 6, 2012 at 9:58 AM, Ned Batchelder wrote: > On 11/6/2012 11:26 AM, R. David Murray wrote: >> >> On Tue, 06 Nov 2012 18:14:38 +0200, Serhiy Storchaka >> wrote: >>> >>> Another counterintuitive (and possible wrong) example: >>> >>> >>> {print('foo'): print('bar')} >>> bar >>>

Re: [Python-Dev] chained assignment weirdity

MRAB wrote: That would make augmented assignment more difficult. For example, how would you write the equivalent of "x -= y"? SUBTRACT x FROM y. CLOSE POST WITH SMILEY. -- Greg ___ Python-Dev mailing list Python-Dev@python.org http://mail.python.org

Re: [Python-Dev] chained assignment weirdity

On 11/6/2012 1:19 PM, Devin Jeanpierre wrote: On Nov 6, 2012 1:05 PM, "Ned Batchelder" > wrote: > > On 11/6/2012 11:26 AM, R. David Murray wrote: >> >> On Tue, 06 Nov 2012 18:14:38 +0200, Serhiy Storchaka mailto:storch...@gmail.com>> wrote: >>> >>> Another cou

Re: [Python-Dev] chained assignment weirdity

On Nov 6, 2012 1:05 PM, "Ned Batchelder" wrote: > > On 11/6/2012 11:26 AM, R. David Murray wrote: >> >> On Tue, 06 Nov 2012 18:14:38 +0200, Serhiy Storchaka wrote: >>> >>> Another counterintuitive (and possible wrong) example: >>> >>> >>> {print('foo'): print('bar')} >>> bar >>> foo >

Re: [Python-Dev] chained assignment weirdity

On 11/6/2012 11:26 AM, R. David Murray wrote: On Tue, 06 Nov 2012 18:14:38 +0200, Serhiy Storchaka wrote: Another counterintuitive (and possible wrong) example: >>> {print('foo'): print('bar')} bar foo {None: None} http://bugs.python.org/issue11205 This seems to me better l

Re: [Python-Dev] chained assignment weirdity

On Tue, 06 Nov 2012 18:14:38 +0200, Serhiy Storchaka wrote: > Another counterintuitive (and possible wrong) example: > >>>> {print('foo'): print('bar')} >bar >foo >{None: None} http://bugs.python.org/issue11205 --David ___ Python-Dev

Re: [Python-Dev] chained assignment weirdity

On 06.11.12 14:01, Nick Coghlan wrote: Python, on the other hand, is able to preserve primarily left to right evaluation in this case with only the far right hand expression needing to be evaluated out of order. I'm surprised, but it is really so. >>> {}[print('foo')] = print('bar') bar

Re: [Python-Dev] chained assignment weirdity

+1 to what Nick said. And I thought about this carefully when designing the language. It's not a bug. The note about assignment RHS being evaluated before LHS is normative -- you just have to interpret RHS as "after the *last* '=' symbol". Assignment itself is *not* an expression. On Tue, Nov 6, 2

Re: [Python-Dev] chained assignment weirdity

On 2012-11-06 15:02, Rob Cliffe wrote: On 06/11/2012 12:01, Nick Coghlan wrote: As noted, it's really only counterintuitive if your intuition is primed to expect C style right to left chained assignments. Python, on the other hand, is able to preserve primarily left to right evaluation in thi

Re: [Python-Dev] chained assignment weirdity

On 06/11/2012 12:01, Nick Coghlan wrote: As noted, it's really only counterintuitive if your intuition is primed to expect C style right to left chained assignments. Python, on the other hand, is able to preserve primarily left to right evaluation in this case with only the far right hand e

Re: [Python-Dev] chained assignment weirdity

As noted, it's really only counterintuitive if your intuition is primed to expect C style right to left chained assignments. Python, on the other hand, is able to preserve primarily left to right evaluation in this case with only the far right hand expression needing to be evaluated out of order.

Re: [Python-Dev] chained assignment weirdity

On 11/6/2012 1:18 AM, Chris Withers wrote: Hi All, I bumped into this using Michael Foord's Mock library. It feels like a bug to me, but thought I'd ask here before logging one in the tracker in case people know that we won't be able to fix it: On 05/11/2012 13:43, Michael Foord wrote: class

Re: [Python-Dev] chained assignment weirdity

On Tue, Nov 6, 2012 at 1:18 AM, Chris Withers wrote: > Hi All, > > I bumped into this using Michael Foord's Mock library. > It feels like a bug to me, but thought I'd ask here before logging one in > the tracker in case people know that we won't be able to fix it: > > On 05/11/2012 13:43, Michael

[Python-Dev] chained assignment weirdity

Hi All, I bumped into this using Michael Foord's Mock library. It feels like a bug to me, but thought I'd ask here before logging one in the tracker in case people know that we won't be able to fix it: On 05/11/2012 13:43, Michael Foord wrote: class Foo(object): ... def __setattr__(s, k,