[Python-3000] PEP 3132: Extended Iterable Unpacking (original) (raw)

Chris Rebert cvrebert at gmail.com
Wed May 2 03:51:24 CEST 2007

In the interest of furthering the discussion, here are two past threads on similar suggestions:

[Python-Dev] Half-baked proposal: * (and **?) in assignments http://mail.python.org/pipermail/python-dev/2002-November/030349.html

[Python-ideas] Javascript Destructuring Assignment http://mail.python.org/pipermail/python-ideas/2007-March/000284.html

On 5/1/07, Christian Heimes <lists at cheimes.de> wrote:

Neville Grech Neville Grech wrote: > This reminds me a lot of haskell/prolog's head/tail list splitting. Looks > like a good feature.

Agreed! > a*=range(5) > hmmn maybe in such a case, whenever there is the * operator, the resulting > item is always a list/tuple, like the following: > a=[[0,1,2,3,4]] ? Did you mean *a = range(5)? The result is too surprising for me. I would suspect that *a = range(5) has the same output as a = range(5). >>> *b = (1, 2, 3) >>> b (1, 2, 3) >>> a, *b = (1, 2, 3) >>> a, b 1, (2, 3) >>> *b, c = (1, 2, 3) >>> b, c (1, 2), 3

>>> a, *b, c = (1, 2, 3) >>> a, b, c 1, (2,), 3 But what would happen when the right side is too small? >>> a, *b, c = (1, 2) >>> a, b, c 1, (), 2 or should it raise an unpack exception? This should definitely raise an exception >>> a, *b, c, d = (1, 2) Christian

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