2018-05-23 17:54 GMT+03:00 Mike Miller <python-ideas@mgmiller.net>:

On 2018-05-22 14:32, Kirill Balunov wrote:

    # in global scope everything works ok since locals is globals
     >>> while len( this( val = dummy() ) ) >= 0:
    ...     print(val)
    [0, 1]
    [0, 1, 2]
    [0, 1, 2, 3]

Interesting!  Although the example with a len() and mutable default arguments obscured the utility, I thought.  Also, why limit it to one assignment?

I just want some dummy example which can not be trivially handled with `for name in iter(func, value)`. But the latter is also only partly true. You can make something like: 

class P:

    __slots__ = ('func')

    def __init__(self, func):

        self.func = func    

    def __eq__(self, other):

        return not self.func(other)

for val in iter(dummy, P(lambda x: len(x) < 5)):

    print(val)

[0, 1]

[0, 1, 2]

[0, 1, 2, 3]

The only restriction is that you can not pass arguments to a `func`, but this, to some extent, can also be handled with lambda. I limit it to _one assignment_ firstly to make it simple, and secondly to get rid of some edge cases.

 

Liked Terry's suggestions for name.  The name that jumped into my brain as I read was a reuse of the locals() or globals() callable with key words, that would change their behavior to what you suggest.

I like `this` because it is easy to follow in my opinion: " While this name assigned to an expression is  greater than zero do... " But of course I'm open to any other spelling. I'm just wondering, if someone like this form as an alternative for assignment expression (`:=`).

With kind regards,

-gdg

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