On Thu, Jul 27, 2000 at 10:10:51AM -0700, Ka-Ping Yee wrote:
On Thu, 27 Jul 2000, Guido van Rossum wrote:
The basic slice form is:
a[i:j] += b
What does this mean? I don't see how it could be any different from:
a[j:j] = b
a[i:j] += b means exactly the same as: a[i:j] = a[i:j] + b Whether it does anything other than raising an exception depends entirely on the types of a and b !
I can't even imagine what the simpler case
a[i:j:k] += 1
would do... unless you wish to propose element-wise operators (e.g. add 1 to each of the elements that would participate in the slice)
That's entirely user-defined. Augmented assignment simply extends Pythons extremely liberal (my cultural heritage tempts me to say 'communist';) semantics in these cases. a[i:j:k] += 1 is exactly a[i:j:k] = a[i:j:k] + 1 If 'a' is a Python class, this would turn into (forgetting about order of evaluation, for a second): a.__setitem__(slice(i, j, k), a[slice(i, j, k)].__add_ab__(1))
It looks to me like going through various contortions to support augmented assignment to slices is not going to be worth the trouble.
May i suggest
>>> a[i:j] += b SyntaxError: augmented assignment to a slice is not allowed
Sure, but it doesn't make sense unless 'a[i:j] = a[i:j] + b' raises similar problems. Why this arbitrary border ? Because you can't imagine people wanting it ? -- Thomas Wouters <thomas@xs4all.net> Hi! I'm a .signature virus! copy me into your .signature file to help me spread!