Re: [Python-Dev] Adding bytes.frombuffer() constructor to PEP 467 (was: [Python-ideas] Adding bytes.frombuffer() constructor

2016-10-25 Thread Nick Coghlan
On 25 October 2016 at 02:53, Chris Barker  wrote:
> IS this na either-or? IF someone is proposing a nice lib for "low level data
> buffer
> manipulation", then yes, putting frombuffer() in there would be a fine idea.
>
> But if there is no such proposal on the table, then I think adding a
> frombuffer method to the bytes object is a small improvement that we can do
> now.

The suggestion came from folks working on asyncio performance
improvements, and we already got the entire ``selectors`` abstraction
from the original asyncio implementation work, as well as Yury's new
libuv-based ``uvloop`` asyncio event loop implementation.

Given that "make OpenStack/SDN/NFV run faster" is a key point of
interest for folks like Intel and Red Hat, I'm *absolutely* suggesting
that they put some paid time and energy into a lower level buffer
manipulation library between now and the Python 3.7 feature freeze in
12+ months, as I think that will have longer term pay-offs well beyond
the scope of the original use cases :)

Cheers,
Nick.

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Nick Coghlan   |   [email protected]   |   Brisbane, Australia
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Re: [Python-Dev] Adding bytes.frombuffer() constructor to PEP 467 (was: [Python-ideas] Adding bytes.frombuffer() constructor

2016-10-25 Thread Nick Coghlan
On 25 October 2016 at 17:25, Nick Coghlan  wrote:
> as well as Yury's new
> libuv-based ``uvloop`` asyncio event loop implementation.

Oops, I phrased that badly - the default asyncio event loop
implementation is still pure Python, but uvloop is a drop-in Cython
based replacement.

Cheers,
Nick.

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Nick Coghlan   |   [email protected]   |   Brisbane, Australia
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[Python-Dev] Default formatting

2016-10-25 Thread Serhiy Storchaka
Classes that doesn't define the __format__ method for custom PEP 3101 
formatting inherits it from parents.


Originally the object.__format__ method was designed as [1]:

def __format__(self, format_spec):
return format(str(self), format_spec)

An instance is converted to string and resulting string is formatted 
according to format specifier.


Later this design was reconsidered [2], and now object.__format__ is 
equivalent to:


def __format__(self, format_spec):
assert format_spec == ''
return format(str(self), '')

Non-empty format specifier is rejected.

But why call format() on resulting string? Why not return resulting 
string as is? object.__format__ could be simpler (not just 
implementation, but for understanding):


def __format__(self, format_spec):
assert format_spec == ''
return str(self)

This can change the behaviour in corner case. str(self) can return not 
exact string, but string subclass with overloaded __format__. But I 
think we can ignore such subtle difference.


[1] https://www.python.org/dev/peps/pep-3101/
[2] http://bugs.python.org/issue7994

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Re: [Python-Dev] Adding bytes.frombuffer() constructor to PEP 467 (was: [Python-ideas] Adding bytes.frombuffer() constructor

2016-10-25 Thread Chris Barker
On Tue, Oct 25, 2016 at 12:25 AM, Nick Coghlan  wrote:

> The suggestion came from folks working on asyncio performance
> improvements,




>  I'm *absolutely* suggesting
> that they put some paid time and energy into a lower level buffer
> manipulation library between now and the Python 3.7 feature freeze in
> 12+ months, as I think that will have longer term pay-offs well beyond
> the scope of the original use cases :)
>

Sounds good -- let's hope something comes of that.

-CHB




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