On Wed, Dec 1, 2021 at 10:30 PM André Roberge andre.roberge@gmail.com wrote:
On Wed, Dec 1, 2021 at 2:17 AM Chris Angelico rosuav@gmail.com wrote:
I've just updated PEP 671 https://www.python.org/dev/peps/pep-0671/ with some additional information about the reference implementation, and some clarifications elsewhere.
*PEP 671: Syntax for late-bound function argument defaults*
Questions, for you all:
- If this feature existed in Python 3.11 exactly as described, would
you use it?
Currently, I'm thinking "absolutely not".
However, I thought the same about the walrus operator and I now miss not being able to use it in a program that includes support for Python 3.6 and where I have literally dozens of places where I would use it if I could.
Very fair :)
- Independently: Is the syntactic distinction between "=" and "=>" a
cognitive burden?
Yes. I really think that using a keyword like defer, or from_calling_scope ;-), would significantly reduce the cognitive burden.
Also fair. I'm not a fan of keywords for this sort of thing, since it implies that you could do this:
def f(x=defer []): ...
dflt = defer [] def f(x=dflt): ...
which is a completely different proposal (eg it would be evaluated only when you "touch" that, rather than being guaranteed to be evaluated before the first line of the function body). That's why I want to adorn the equals sign and nothing else.
- If "no" to question 1, is there some other spelling or other small
change that WOULD mean you would use it? (Some examples in the PEP.)
*Perhaps* if a keyword would be used instead of symbols, I might reconsider.
I find the emphasis of trying to cram too much information in single lines of code to be really a burden. Many years ago, I argued very unsuccessfully for using a 'where:' code block for annotations. (To this day, I still believe it would make the code much more readable, at the cost of a slight duplication.) Using what is at first glance a cryptic operator like => for late binding is not helping readability, especially when type annotations are thrown in the mix.
Aside: at the same time, I can see how using => instead of lambda as a potential win in readability, including for beginners.
It's interesting how different people's views go on that sort of thing. It depends a lot on how much people expect to use something. Features you use a lot want to have short notations, features you seldom use are allowed to have longer words.
- Do you know how to compile CPython from source, and would you be
willing to try this out? Please? :)
Sorry, I'm not interested enough at this point but, given the amount of work you put into this, I decided that the least I could do is provide feedback rather than be a passive reader.
That's absolutely fine. I don't by any means expect everyone to be able or willing to compile CPython. Feedback is absolutely appreciated, and I asked the question with full expectation of getting a few "No" responses :)
Thank you for taking the time to respond. Thoughtful feedback is incredibly helpful.
ChrisA