On Sun, Oct 23, 2016 at 6:15 AM, Steve D'Aprano
wrote:
> On Sun, 23 Oct 2016 01:15 pm, eryk sun wrote:
>
>> I meant the behavior seems to have been copied to align with generator
>> expressions, even though the cited rationale doesn't apply. I'm not
>> saying this is wrong. It's useful that the ex
On Sun, 23 Oct 2016 02:24 pm, Chris Angelico wrote:
> 1) Sometimes, all the iterables can be evaluated in advance.
>
> dice_2d6 = [a+b for a in range(1,7) for b in range(1,7)]
>
> 2) But sometimes, subsequent iterables depend on the outer loop.
>
> triangle = [a+b for a in range(1, 7) for b in
On Sun, 23 Oct 2016 01:15 pm, eryk sun wrote:
> I meant the behavior seems to have been copied to align with generator
> expressions, even though the cited rationale doesn't apply. I'm not
> saying this is wrong. It's useful that the expression for the outer
> iterator is evaluated in the defining
On Sun, Oct 23, 2016 at 4:08 PM, eryk sun wrote:
> For generator expressions, it's about early binding of the outer
> iterator. This makes the result of the expression for the outer
> iterator behave like a function parameter. Obviously it has to be
> evaluated in the defining scope. Comprehension
On 10/22/2016 11:24 PM, Chris Angelico wrote:
On Sun, Oct 23, 2016 at 2:14 PM, Steve D'Aprano
wrote:
But it seems that the first iterator (and only that one) is evaluated
in the parent context:
Because the first iterator *can* always be evaluated.
I don't understand what you mean by that. I
On Sun, Oct 23, 2016 at 3:44 AM, Steve D'Aprano
wrote:
>
> https://www.python.org/dev/peps/pep-0289/#early-binding-versus-late-binding
>
> But this isn't a question about early or late binding, it is asking why the
> variable y is treated as both global and local in the same comprehension.
> This
On Sun, 23 Oct 2016 11:51 am, eryk sun wrote:
> On Sat, Oct 22, 2016 at 11:57 PM, Chris Angelico wrote:
>>
>> Normally, a comprehension is described as being equivalent to an
>> unrolled loop, inside a nested function.
>> ...
>> But it seems that the first iterator (and only that one) is evaluate
On Sun, Oct 23, 2016 at 2:14 PM, Steve D'Aprano
wrote:
> There's definitely something strange going on. Compare the what happens when
> the semi-global variable is in the first loop iterable versus the second
> loop iterable. In this first example, y refers to both the global and the
> local, yet
On Sun, Oct 23, 2016 at 2:14 PM, Steve D'Aprano
wrote:
>>> But it seems that the first iterator (and only that one) is evaluated
>>> in the parent context:
>>
>> Because the first iterator *can* always be evaluated.
>
> I don't understand what you mean by that. If I take you literally, it is
> obv
On Sun, 23 Oct 2016 11:43 am, Terry Reedy wrote:
> On 10/22/2016 7:57 PM, Chris Angelico wrote:
>> This surprised me.
>>
>> Python 3.4.2 (default, Oct 8 2014, 10:45:20)
>> [GCC 4.9.1] on linux
>> Type "help", "copyright", "credits" or "license" for more information.
> y=6
> [(x,y) for x i
On Sun, 23 Oct 2016 10:57 am, Chris Angelico wrote:
> This surprised me.
>
> Python 3.4.2 (default, Oct 8 2014, 10:45:20)
> [GCC 4.9.1] on linux
> Type "help", "copyright", "credits" or "license" for more information.
y=6
[(x,y) for x in range(y) for y in range(3)]
> [(0, 0), (0, 1), (
On Sun, Oct 23, 2016 at 1:28 AM, Chris Angelico wrote:
>
> Fair enough, except that a generator expression is syntactic sugar for
> a generator function, and the return value of a generator function is
> a generator object that hasn't yet been started. So where the boundary
> is, then, is a bit of
On Sun, Oct 23, 2016 at 11:51 AM, eryk sun wrote:
> It matches the behavior of generator expressions, for which Guido
> gives the following example, as quoted in PEP 289:
>
> Consider sum(x for x in foo()). Now suppose there's a bug in foo()
> that raises an exception, and a bug in sum() t
On Sun, Oct 23, 2016 at 11:43 AM, Terry Reedy wrote:
>> Normally, a comprehension is described as being equivalent to an
>> unrolled loop, inside a nested function. That would be like this:
>>
>> def temp():
>> ret = []
>> for x in range(y):
>> for y in range(3):
>> ret
On Sat, Oct 22, 2016 at 11:57 PM, Chris Angelico wrote:
>
> Normally, a comprehension is described as being equivalent to an
> unrolled loop, inside a nested function.
> ...
> But it seems that the first iterator (and only that one) is evaluated
> in the parent context:
>
> Why is this? It seems r
On 10/22/2016 7:57 PM, Chris Angelico wrote:
This surprised me.
Python 3.4.2 (default, Oct 8 2014, 10:45:20)
[GCC 4.9.1] on linux
Type "help", "copyright", "credits" or "license" for more information.
y=6
[(x,y) for x in range(y) for y in range(3)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1,
This surprised me.
Python 3.4.2 (default, Oct 8 2014, 10:45:20)
[GCC 4.9.1] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> y=6
>>> [(x,y) for x in range(y) for y in range(3)]
[(0, 0), (0, 1), (0, 2), (1, 0), (1, 1), (1, 2), (2, 0), (2, 1), (2,
2), (3, 0), (3,
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