[Python-Dev] re: for in dict (user expectation poll)

[Thomas Wouters]

On Mon, Feb 05, 2001 at 02:22:50PM -0500, Greg Wilson wrote:

> OK, now here's the hard one.  Clearly,

Noshit. I ran into all of this while trying to figure out how to quick-hack
implement it. My brain exploded while trying to grasp all implications,
which is why I've been quiet on this issue -- I'm healing ;-P

> (a) for i in someList:
> has to continue to mean "iterate over the values".  We've agreed that:

> (b) for k:v in someDict: means "iterate through the items".  (a) looks
> like a special case of (b).

I'm still not sure if I like the special syntax to iterate over
dictionaries. Are we talking about iterators, or about special syntax to use
said iterators in the niche application of dicts and mapping interfaces ? :)

> I therefore asked my colleagues to guess what:

> (c) for x in someDict:

> did.  They all said, "Iterates through the _values_ in the dict",
> by analogy with (a).

But how baffled were they when it didn't do what they expected it to do ?
Did they go, 'oh shit, now what' ? 

> I then asked, "How do you iterate through the keys in a dict, or
> the indices in a list?"  They guessed:

> (d) for x: in someContainer:

Again, how baffled were they when you said it wasn't going to work ? Because
(c) and (d) are just very light syntactic powdered sugar substitutes for
'k:v' where you just don't use one of the two. The extra name binding
operation isn't going to cost you enough to really worry about, IMHO. 

-- 
Thomas Wouters <thomas@xs4all.net>

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