Re: [Python-Dev] PEP 492 quibble and request

2015-05-03 Thread Arnaud Delobelle 
On 1 May 2015 at 20:59, Guido van Rossum  wrote:
> On Fri, May 1, 2015 at 12:49 PM, Ron Adam  wrote:
>>
>>
>> Another useful async function might be...
>>
>>async def yielding():
>>pass
>>
>> In a routine is taking very long time, just inserting "await yielding()"
>> in the long calculation would let other awaitables run.
>>
> That's really up to the scheduler, and a function like this should be
> provided by the event loop or scheduler framework you're using.

Really?  I was under the impression that 'await yielding()' as defined
above would actually not suspend the coroutine at all, therefore not
giving any opportunity for the scheduler to resume another coroutine,
and I thought I understood the PEP well enough.  Does this mean that
somehow "await x" guarantees that the coroutine will suspend at least
once?

To me the async def above was the equivalent of the following in the
'yield from' world:

def yielding():
return
yield # Just to make it a generator

Then "yield from yielding()" will not yield at all - which makes its
name rather misleading!

-- 
Arnaud
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Re: [Python-Dev] Sub-claasing pathlib.Path seems impossible

2015-05-03 Thread Ryan Gonzalez 
http://stackoverflow.com/a/29880095/2097780

My favorite thing about Python is that it's so easy to be evil. ;)


On Fri, May 1, 2015 at 2:30 PM, Christophe Bal  wrote:

> Hello.
>
> In this post
> ,
> I have noticed a problem with the following code.
>
> from pathlib import Path
>> class PPath(Path):
>> def __init__(self, *args, **kwargs):
>> super().__init__(*args, **kwargs)
>>
>> test = PPath("dir", "test.txt")
>>
>>
> This gives the following error message.
>
>
>
>> Traceback (most recent call last):
>>   File "/Users/projetmbc/test.py", line 14, in 
>> test = PPath("dir", "test.txt")
>>   File "/anaconda/lib/python3.4/pathlib.py", line 907, in __new__
>> self = cls._from_parts(args, init=False)
>>   File "/anaconda/lib/python3.4/pathlib.py", line 589, in _from_parts
>> drv, root, parts = self._parse_args(args)
>>   File "/anaconda/lib/python3.4/pathlib.py", line 582, in _parse_args
>> return cls._flavour.parse_parts(parts)AttributeError: type object 
>> 'PPath' has no attribute '_flavour'
>>
>>
> This breaks the sub-classing from Python point of view. In the post
> ,
> I give a hack to sub-class Path but it's a bit Unpythonic.
>
> *Christophe BAL*
> *Enseignant de mathématiques en Lycée **et développeur Python amateur*
> *---*
> *French math teacher in a "Lycée" **and **Python **amateur developer*
>
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-- 
Ryan
[ERROR]: Your autotools build scripts are 200 lines longer than your
program. Something’s wrong.
http://kirbyfan64.github.io/
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Re: [Python-Dev] PEP 492: async/await in Python; version 4

2015-05-03 Thread Steven D'Aprano 
On Fri, May 01, 2015 at 09:24:47PM +0100, Arnaud Delobelle wrote:

> I'm not convinced that allowing an object to be both a normal and an
> async iterator is a good thing.  It could be a recipe for confusion.

In what way?

I'm thinking that the only confusion would be if you wrote "async for" 
instead of "for", or vice versa, and instead of getting an exception you 
got the (a)syncronous behaviour you didn't want.

But I have no intuition for how likely it is that you could write an 
asyncronous for loop, leave out the async, and still have the code do 
something meaningful.

Other than that, I think it would be fine to have an object be both a 
syncronous and asyncronous iterator. You specify the behaviour you want 
by how you use it. We can already do that, e.g. unittest's assertRaises 
is both a test assertion and a context manager.

Objects can have multiple roles, and it's not usually abused, or 
confusing. I'm not sure that async iterables will be any different.



-- 
Steve
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Re: [Python-Dev] Sub-claasing pathlib.Path seems impossible

2015-05-03 Thread Guido van Rossum 
It does sound like subclassing Path should be made easier.

On Sat, May 2, 2015 at 1:30 PM, Ryan Gonzalez  wrote:

> http://stackoverflow.com/a/29880095/2097780
>
> My favorite thing about Python is that it's so easy to be evil. ;)
>
>
> On Fri, May 1, 2015 at 2:30 PM, Christophe Bal 
> wrote:
>
>> Hello.
>>
>> In this post
>> ,
>> I have noticed a problem with the following code.
>>
>> from pathlib import Path
>>> class PPath(Path):
>>> def __init__(self, *args, **kwargs):
>>> super().__init__(*args, **kwargs)
>>>
>>> test = PPath("dir", "test.txt")
>>>
>>>
>> This gives the following error message.
>>
>>
>>
>>> Traceback (most recent call last):
>>>   File "/Users/projetmbc/test.py", line 14, in 
>>> test = PPath("dir", "test.txt")
>>>   File "/anaconda/lib/python3.4/pathlib.py", line 907, in __new__
>>> self = cls._from_parts(args, init=False)
>>>   File "/anaconda/lib/python3.4/pathlib.py", line 589, in _from_parts
>>> drv, root, parts = self._parse_args(args)
>>>   File "/anaconda/lib/python3.4/pathlib.py", line 582, in _parse_args
>>> return cls._flavour.parse_parts(parts)AttributeError: type object 
>>> 'PPath' has no attribute '_flavour'
>>>
>>>
>> This breaks the sub-classing from Python point of view. In the post
>> ,
>> I give a hack to sub-class Path but it's a bit Unpythonic.
>>
>> *Christophe BAL*
>> *Enseignant de mathématiques en Lycée **et développeur Python amateur*
>> *---*
>> *French math teacher in a "Lycée" **and **Python **amateur developer*
>>
>> ___
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>> https://mail.python.org/mailman/listinfo/python-dev
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>>
>>
>
>
> --
> Ryan
> [ERROR]: Your autotools build scripts are 200 lines longer than your
> program. Something’s wrong.
> http://kirbyfan64.github.io/
>
>
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>


-- 
--Guido van Rossum (python.org/~guido)
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