Re: [Python-Dev] cpython (2.7): note Ellipsis syntax

2011-07-31 Thread Georg Brandl
On 07/30/11 19:25, Benjamin Peterson wrote:
 2011/7/30 Georg Brandl g.bra...@gmx.net:
 On 07/30/11 17:00, benjamin.peterson wrote:
 http://hg.python.org/cpython/rev/402f94edf11b
 changeset:   71637:402f94edf11b
 branch:  2.7
 user:Benjamin Peterson benja...@python.org
 date:Sat Jul 30 09:59:12 2011 -0500
 summary:
   note Ellipsis syntax

 files:
   Doc/library/stdtypes.rst |  2 +-
   1 files changed, 1 insertions(+), 1 deletions(-)


 diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
 --- a/Doc/library/stdtypes.rst
 +++ b/Doc/library/stdtypes.rst
 @@ -2930,7 +2930,7 @@
  supports no special operations.  There is exactly one ellipsis object, 
 named
  :const:`Ellipsis` (a built-in name).

 -It is written as ``Ellipsis``.
 +It is written as ``Ellipsis`` or ``...``.

 In 2.7, this is not true; ``...`` only works in slices there.
 
 I know, but why would you use Ellipsis outside of slices?

I wouldn't, but that's not the point: the wording as it is now will lead readers
to think that they can use the Ellipsis singleton as in Python 3, and they will
complain and report bugs about this.

(Also, there must have been some reason to make ... available everywhere
for Python 3.)

Georg

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Re: [Python-Dev] cpython (2.7): note Ellipsis syntax

2011-07-31 Thread Raymond Hettinger

On Jul 30, 2011, at 11:28 PM, Georg Brandl wrote:

 
 (Also, there must have been some reason to make ... available everywhere
 for Python 3.)
 

It's really nice for stub functions:

def foo(x):
...


Raymond

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Re: [Python-Dev] cpython (2.7): note Ellipsis syntax

2011-07-31 Thread Nick Coghlan
On Sun, Jul 31, 2011 at 4:28 PM, Georg Brandl g.bra...@gmx.net wrote:
 (Also, there must have been some reason to make ... available everywhere
 for Python 3.)

Not really - it just let us ditch some special casing in the
compilation toolchain that *restricted* it to being used in subscripts
(i.e. we were looking at the question from the is there a good
rationale for keeping this arbitrary restriction? angle).

Functionality wise, you could already write 'Ellipsis' everywhere you
would otherwise have written '...' and you still have to write ':' as
'slice(None)' outside the context of a subscript operation.

Although, as Raymond notes, it can make a nice substitute for 'pass'
as a placeholder statement, and can also be used as a placeholder
expression.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncogh...@gmail.com   |   Brisbane, Australia
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Re: [Python-Dev] cpython (2.7): note Ellipsis syntax

2011-07-31 Thread Antoine Pitrou
On Sat, 30 Jul 2011 23:47:36 -0700
Raymond Hettinger raymond.hettin...@gmail.com wrote:
  
  (Also, there must have been some reason to make ... available everywhere
  for Python 3.)
  
 
 It's really nice for stub functions:
 
 def foo(x):
 ...

Using a docstring looks a lot less hackish (and it encourages you to
write a doc!):

def foo(x):
Some stub function.




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Re: [Python-Dev] cpython (2.7): note Ellipsis syntax

2011-07-30 Thread Georg Brandl
On 07/30/11 17:00, benjamin.peterson wrote:
 http://hg.python.org/cpython/rev/402f94edf11b
 changeset:   71637:402f94edf11b
 branch:  2.7
 user:Benjamin Peterson benja...@python.org
 date:Sat Jul 30 09:59:12 2011 -0500
 summary:
   note Ellipsis syntax
 
 files:
   Doc/library/stdtypes.rst |  2 +-
   1 files changed, 1 insertions(+), 1 deletions(-)
 
 
 diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
 --- a/Doc/library/stdtypes.rst
 +++ b/Doc/library/stdtypes.rst
 @@ -2930,7 +2930,7 @@
  supports no special operations.  There is exactly one ellipsis object, named
  :const:`Ellipsis` (a built-in name).
  
 -It is written as ``Ellipsis``.
 +It is written as ``Ellipsis`` or ``...``.

In 2.7, this is not true; ``...`` only works in slices there.

Georg

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Re: [Python-Dev] cpython (2.7): note Ellipsis syntax

2011-07-30 Thread Benjamin Peterson
2011/7/30 Georg Brandl g.bra...@gmx.net:
 On 07/30/11 17:00, benjamin.peterson wrote:
 http://hg.python.org/cpython/rev/402f94edf11b
 changeset:   71637:402f94edf11b
 branch:      2.7
 user:        Benjamin Peterson benja...@python.org
 date:        Sat Jul 30 09:59:12 2011 -0500
 summary:
   note Ellipsis syntax

 files:
   Doc/library/stdtypes.rst |  2 +-
   1 files changed, 1 insertions(+), 1 deletions(-)


 diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
 --- a/Doc/library/stdtypes.rst
 +++ b/Doc/library/stdtypes.rst
 @@ -2930,7 +2930,7 @@
  supports no special operations.  There is exactly one ellipsis object, named
  :const:`Ellipsis` (a built-in name).

 -It is written as ``Ellipsis``.
 +It is written as ``Ellipsis`` or ``...``.

 In 2.7, this is not true; ``...`` only works in slices there.

I know, but why would you use Ellipsis outside of slices?



-- 
Regards,
Benjamin
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Re: [Python-Dev] cpython (2.7): note Ellipsis syntax

2011-07-30 Thread Greg Ewing

Benjamin Peterson wrote:


why would you use Ellipsis outside of slices?


I could imagine someone wanting to use it as part of a
function API. For example,

   print(a, b, c, ...)

would have been a nice way to tell print() not to put
a newline on the end.

--
Greg
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