Re: [Python-ideas] PEP 505: None-aware operators

On Thu, Aug 2, 2018 at 12:04 AM, Jonathan Fine wrote: > Hi Steve > > Thank you for your reply. > > We're discussing the abstract to PEP 505, which writes > === > The "None-aware attribute access" operator ?. ("maybe dot") evaluates > the complete expression if the left hand side evaluates to a

Re: [Python-ideas] PEP 505: None-aware operators

Hi Steve Thank you for your reply. We're discussing the abstract to PEP 505, which writes === The "None-aware attribute access" operator ?. ("maybe dot") evaluates the complete expression if the left hand side evaluates to a value that is not None === I gave (42).str as an example. I wrote >

Re: [Python-ideas] PEP 505: None-aware operators

On Wed, Aug 01, 2018 at 11:03:05AM +0100, Jonathan Fine wrote: [...] > After my last post, you wrote > > None.?__str__ > > produces None, even though None has a __str__ attribute. > > This surprises me. But I think it follows from the rules in >

Re: [Python-ideas] PEP 505: None-aware operators

Hi Stephan You wrote > Let me stand up and claim that if a chain consists *only* of None-coalescing > operations, then breaking up the chain by adding parentheses does not > matter, ever. You missed a post I made, 17 minutes before yours. I then believed that PEP 505 specified. #1. (None ?.

Re: [Python-ideas] PEP 505: None-aware operators

On Wed, Aug 1, 2018 at 7:09 PM, Jonathan Fine wrote: > Hi Chris > > We're discussing. >> 10) a ?. b ?. c >> 11) (a ?. b) ?. c > > I asked >> So, are there any values of 'a' for which #10 and #11 don't give the >> same result? > > You replied >> I'm not prepared to put my neck out and say "They

Re: [Python-ideas] PEP 505: None-aware operators

Op wo 1 aug. 2018 11:10 schreef Jonathan Fine : > > > You're right to be cautious. My understanding of PEP 505 is that > #13. a ?. b ?. __str__ > #14. (a ?. b) ?. __str__ > are not equivalent. The first is None, and the other is None.__str__. > That looks like a gotcha. > No. None.?__str__

Re: [Python-ideas] PEP 505: None-aware operators

Op wo 1 aug. 2018 10:50 schreef Chris Angelico : > On Wed, Aug 1, 2018 at 6:45 PM, Jonathan Fine wrote: > > Hi Chris > > > > Thank you for your reply. I think we're making good progress. > > > > You wrote > > > >>> 10) a ?. b ?. c > >>> 11) (a ?. b) ?. c > >> > >> I would parse those

Re: [Python-ideas] PEP 505: None-aware operators

Hi Chris We're discussing. > 10) a ?. b ?. c > 11) (a ?. b) ?. c I asked > So, are there any values of 'a' for which #10 and #11 don't give the > same result? You replied > I'm not prepared to put my neck out and say "They are absolutely > identical" and have people jump on me with some

Re: [Python-ideas] PEP 505: None-aware operators

On Wed, Aug 1, 2018 at 6:45 PM, Jonathan Fine wrote: > Hi Chris > > Thank you for your reply. I think we're making good progress. > > You wrote > >>> 10) a ?. b ?. c >>> 11) (a ?. b) ?. c >> >> I would parse those differently, but you may be right that they'll >> always have the same final

Re: [Python-ideas] PEP 505: None-aware operators

Hi Chris Thank you for your reply. I think we're making good progress. You wrote >> 10) a ?. b ?. c >> 11) (a ?. b) ?. c > > I would parse those differently, but you may be right that they'll > always have the same final result. I'd like to get some certainty on this. I'm not aware of any

Re: [Python-ideas] PEP 505: None-aware operators

On Wed, Aug 1, 2018 at 6:00 PM, Jonathan Fine wrote: > Hi Chris > > You wrote: > >> Oh. The equivalent ones are #1 and #2, and #7 and #8, where this >> proposal doesn't change anything. Otherwise, they're not equivalent. > > Are you sure. I'd also expect #10 and #11 to be equivalent. > > By the

Re: [Python-ideas] PEP 505: None-aware operators

Hi Chris You wrote: > Oh. The equivalent ones are #1 and #2, and #7 and #8, where this > proposal doesn't change anything. Otherwise, they're not equivalent. Are you sure. I'd also expect #10 and #11 to be equivalent. By the way, there's a typo in my examples: 11) (a .? b) ?. c -- Jonathan

Re: [Python-ideas] PEP 505: None-aware operators

Hi Chris Thank you for your prompt reply. You wrote > Incorrect. The short-circuiting behaviour ends at any sort of > grouping. It's like how "a < b < c" is not equivalent to "(a < b) < > c", nor to "a < (b < c)". You've told me that my answer B is wrong. But you've not provided your correct

Re: [Python-ideas] PEP 505: None-aware operators

On Wed, Aug 1, 2018 at 5:29 PM, Jonathan Fine wrote: > Hi All > > I have two further questions. I'm keen to clarify what is the > behaviour specified by PEP 505. I'm not, at this time, interested in > why and how PEP 505 specifies behaviour. I just wish, through explicit > examples, to clarify

Re: [Python-ideas] PEP 505: None-aware operators

Hi All I have two further questions. I'm keen to clarify what is the behaviour specified by PEP 505. I'm not, at this time, interested in why and how PEP 505 specifies behaviour. I just wish, through explicit examples, to clarify the behaviour that is specified. Here 'a' is an identifier.