[Python-Dev] accumulator display syntax

Phillip J. Eby pje at telecommunity.com
Fri Oct 17 16:38:00 EDT 2003

At 03:20 PM 10/17/03 -0500, Skip Montanaro wrote:
>     * functions
>     * unbound methods
>     * bound methods
>     * generator functions
>     * iterators (currently invisible via syntax, but created by calling a
>       generator function?)
>     * instances magically callable via __call__

The last item on the list encompasses at least the first three.  But you 
also left out __init__ and __new__, which are really ClassType.__call__ or 
type.__call__, though.  :)

To me (and the interpreter, actually), there's just tp_call, tp_iter, and 
tp_iternext (or whatever their actual names are).  Callability, 
iterability, and iterator-next.  Many kinds of objects may have these 
aspects, just as many kinds of objects may be addable with '+'.

Of the things you mention, however, most don't actually have different 
syntax for creating them, and some are even the same object type (e.g. 
unbound and bound methods).  And the syntax for *using* them is always 
uniform: () always calls an object, for ... in ... creates an iterator from 
an iterable, .next() goes to the next item.

>and now this new (rather limited) syntax for creating iterators.

Actually, as now being discussed, list comprehensions would be a special 
case of an iterator expression.

>I am beginning to find it all a bit confusing and unsettling.

Ironically, with iterator comprehension in place, a list comprehension 
would now look like a list containing an iterator, which I agree might be 
confusing.  Too bad we didn't do iterator comps first, or list(itercomp) 
would be the idiomatic way to make a listcomp.

That's really the only confusing bit I see about itercomps...  that you 
have to be careful where you put your parentheses, in order to make your 
intentions clear in some contexts.  However, that's true for many kinds of 
expressions even now.

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