Re: [Python-ideas] Fix some special cases in Fractions?

2018-08-29 Thread Jeroen Demeyer
On 2018-08-30 06:39, Neil Girdhar wrote: I'd like these to be Fraction(1), Fraction(1), and Fraction(0). Why? I cannot think of any natural use case why you would want Fractions for a few special cases on an operation which returns non-Fractions generically. I consider it a feature to know

[Python-ideas] Fix some special cases in Fractions?

2018-08-29 Thread Neil Girdhar
Would there be any problem with changing: In [4]: Fraction(1, 1) ** Fraction(2, 3) Out[4]: 1.0 In [5]: Fraction(-1, 1) ** Fraction(2, 3) Out[5]: (-0.4998+0.8660254037844387j) In [6]: Fraction(0, 1) ** Fraction(2, 3) Out[6]: 0.0 I'd like these to be Fraction(1), Fraction(1), and

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Ethan Furman
On 08/29/2018 04:53 PM, Hugh Fisher wrote: From: Marko Ristin-Kaufmann: There seems to be evidence that design-by-contract is useful. Let me cite Bertrand Meyer from his article "Why not program right?" that I already mentioned before: I don't think that being useful by itself should be

[Python-ideas] zipfile encryption function

2018-08-29 Thread 大野隆弘
Dear all, I would like to use zipfile encryption as python standard library. https://github.com/python/cpython/blob/master/Lib/zipfile.py Below document says "currently" cannot. https://github.com/python/cpython/blob/master/Doc/library/zipfile.rst "but it currently cannot create an encrypted

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Hugh Fisher
> Date: Thu, 30 Aug 2018 00:07:04 +0200 > From: Marko Ristin-Kaufmann ... > I think we got entangled in a discussion about whether design-by-contract > is useful or not. IMO, the personal experience ("I never used/needed this > feature") is quite an inappropriate rule whether something needs to

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Eric V. Smith
On 8/29/2018 6:39 PM, Eric Fahlgren wrote: On Wed, Aug 29, 2018 at 3:07 PM Marko Ristin-Kaufmann mailto:marko.ris...@gmail.com>> wrote: Could you please elaborate a bit? I don't see how the annotations would make the contracts invoked on inheritance. Consider this simple case:

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Ivan Levkivskyi
replying to the list now... On Thu, 30 Aug 2018 at 00:11, Ivan Levkivskyi wrote: > On Wed, 29 Aug 2018 at 13:18, Steven D'Aprano wrote: > >> I didn't want to embarass Ivan any further by seemingly picking on his >> opinion about contracts being always statically checked, but when I >> asked

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread David Mertz
The technique Eric suggests is probably better than what I had in mind. But I was thinking you could have an "inherit" decorator for methods (or for a class as a whole). It's easy enough for a decorator to attach a `.__contracts__` attribute to either the class or the individual methods. Then the

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Greg Ewing
Jonathan Fine wrote: My message of support for Ivan quoted the Eiffel docs. https://www.eiffel.org/doc/eiffel/ET-_Design_by_Contract_%28tm%29%2C_Assertions_and_Exceptions During development and testing, assertion monitoring should be turned on at the highest possible level. Combined with

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Steven D'Aprano
On Wed, Aug 29, 2018 at 02:26:54PM +0100, Jonathan Fine wrote: > This is about a difference of opinion regarding design by contract and > static checking, that Steve D'Aprano has re-raised. Steve wrote that > Ivan Levkivskyi's opinion was that: > > > contracts [are] always statically checked >

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Jonathan Fine
This is about a difference of opinion regarding design by contract and static checking, that Steve D'Aprano has re-raised. Steve wrote that Ivan Levkivskyi's opinion was that: > contracts [are] always statically checked This is what Ivan wrote: > TBH, I think one of the main points of design by

Re: [Python-ideas] Python-ideas Digest, Vol 141, Issue 145

2018-08-29 Thread Paul Moore
On Wed, 29 Aug 2018 at 13:26, Steven D'Aprano wrote: > > [steve@ando ~]$ pip install numpy > Collecting numpy > /usr/local/lib/python3.5/site-packages/pip/_vendor/requests/packages/urllib3/util/ssl_.py:315: > SNIMissingWarning: An HTTPS request has been made, but the SNI (Subject > Name

Re: [Python-ideas] Python-ideas Digest, Vol 141, Issue 145

2018-08-29 Thread Paul Moore
On Wed, 29 Aug 2018 at 13:17, Oscar Benjamin wrote: > Scipy (on Windows) is a different story. There are Windows (and other platform) wheels for scipy 1.1.0 on PyPI, so that's easy too :-) Paul ___ Python-ideas mailing list Python-ideas@python.org

Re: [Python-ideas] Python-ideas Digest, Vol 141, Issue 145

2018-08-29 Thread Steven D'Aprano
On Wed, Aug 29, 2018 at 01:15:46PM +0100, Oscar Benjamin wrote: > On Tue, 28 Aug 2018 at 08:12, Jacco van Dorp wrote: > > > > Op ma 27 aug. 2018 om 23:18 schreef James Lu : > >> > >> > As Matthew points out, you could use numpy.array. Or code your own > >> > class, by providing __add__ and

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Steven D'Aprano
I didn't want to embarass Ivan any further by seemingly picking on his opinion about contracts being always statically checked, but when I asked off-list I got told to reword and post it here. So here it is. Sorry Ivan if this makes you feel I'm picking on you, that isn't my intention. On

Re: [Python-ideas] Python-ideas Digest, Vol 141, Issue 145

2018-08-29 Thread Oscar Benjamin
On Tue, 28 Aug 2018 at 08:12, Jacco van Dorp wrote: > > Op ma 27 aug. 2018 om 23:18 schreef James Lu : >> >> > As Matthew points out, you could use numpy.array. Or code your own >> > class, by providing __add__ and __iadd__ methods. >> >> I could, but I don't think that justifies not having this

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Steven D'Aprano
On Wed, Aug 29, 2018 at 09:23:02AM +0200, Jacco van Dorp wrote: > Op wo 29 aug. 2018 om 03:59 schreef Steven D'Aprano : > > > On Tue, Aug 28, 2018 at 07:46:02AM +0200, Marko Ristin-Kaufmann wrote: > > > Hi, > > > To clarify the benefits of the contracts, let me give you an example from > > > our

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Steven D'Aprano
On Wed, Aug 29, 2018 at 05:52:46PM +1200, Greg Ewing wrote: > Wes Turner wrote: > >I'm going to re-write that in a pseudo-Eiffel like syntax: > > Maybe some magic could be done to make this work: > > def __init__(self, img: np.ndarray, x: int, y: int, width: int, > height:

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Jacco van Dorp
Op wo 29 aug. 2018 om 03:59 schreef Steven D'Aprano : > On Tue, Aug 28, 2018 at 07:46:02AM +0200, Marko Ristin-Kaufmann wrote: > > Hi, > > To clarify the benefits of the contracts, let me give you an example from > > our code base: > > > > @icontract.pre(lambda x: x >= 0) > >

Re: [Python-ideas] Pre-conditions and post-conditions

2018-08-29 Thread Brice Parent
I've never used contracts, so excuse me if I didn't get how they would work, and what they should do. The last example is about pre-post conditions in a class constructor. But I imagine this is not the only case where one would want to define contracts, like probably: within methods that