On 5/10/2011 3:22 AM, Algis Kabaila wrote:
On Tuesday 10 May 2011 11:25:59 Terry Reedy wrote:
> class listwrap:
> def __init__(self, lis):
> self._list = lis
> def __getitem__(self, dex):
> i,j = dex
> return self._list[i][j]
> # __setitem__: exercise for reader
> l = listwrap([[1,2,3],['a','b','c']])
> print(l[0,2],l[1,0])
> # 3 a
Thank you for your response. I have to confess that I do have the cludge
of an answer to my own quesion, but it is a cludge; Your method looks
much better, though I don't think it is complete - this subclassing of
__getitem__ appears to stop simple list access, i.e. if li = [1, 2 ,3],
it seems to me that print(li[2]) would raise an exception, no?
Yes, there really should be a guard condition: if isinstance(x tuple)
or try: len(x) == 2. A __getattr__ method could be added to forwar other
list methods to the wrapped list. One could try subclassing instead of
wrapping, but some special methods have a fast path access for builtins
that bypasses subclass methods. I think __getitem__ may be one such.
Wrapping is safe in that respect.
--
Terry Jan Reedy
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