PEP 572: Python assignment expressions has been accepted

(groups.google.com)

317 points est | 1 comments | 03 Jul 18 08:30 UTC | HN request time: 0.208s | source

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amelius ◴[03 Jul 18 09:55 UTC] No.17448876[source]▶

If they add anything to Python, it should be the ability to do functional-style programming without hassle. Right now it's almost impossible to compose functions in an inline style such as used in functional programming languages. Yes, there's lambda, but it doesn't extend into multiple lines, and applying a function to a bunch of lambdas directly leads to line-width overflow. Even JavaScript has better support for functional-style programming. Perhaps Guido should spend a year writing Haskell :)

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i_do_not_agree ◴[03 Jul 18 10:16 UTC] No.17448972[source]▶

>>17448876 #

Just need something like blocks in Smalltalk. Wikipedia page on list comprehensions says Smalltalk-80 had list comprehensions and that was ~ 40 years ago.

Smalltalk also uses ":=" for assignment and "=" for comparison. In Pharo, VA and Dolphin at least does what this Python proposal does - return the value of the last expression.

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1. dfox ◴[03 Jul 18 21:15 UTC] No.17453671[source]▶

>>17448972 #

Smalltalk (and for that matter Ruby) has weird feature that blocks and methods are different different concepts.

In my opinion the Python's explicit self argument is somehow cleaner approach than having distinct block and function/method types. You still need some kind of ugliness in order to implement super(), but for Python 3 that happens at compile time and the resulting syntax is reasonably sane.

As for the aforementioned method context issue CLOS/MOP takes interesting approach of macroexpanding the method definition into something like

  (lambda (args next-method)
    (labels
      ((call-next-method &args)
        ...
        (funcall next-method ...)))
      (impl (...)
        ... method body ...))
     (funcall impl args)))

Also of note is that in ST, there are no control structures, even if is implemented as method on Boolean instances which takes block argument, with true and false being instances of True resp. False with different implementations of #ifTrue: method.

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