On 02/01/13 16:55, Dave Angel wrote:
On 01/02/2013 11:41 AM, Steven D'Aprano wrote:
The bit about __index__ refers to using trunc():
OK, that partially solves it :-)
I don't know what this "index() builtin" is, it doesn't appear to exist.
That was also what confused me. The only indexz() I could find was the
one that found the index of an item in a collection
>>> [1,2,3].index(2)
1
And I didn't see how trunc() or division helped there...
But __index__ is a special method that converts to int without rounding
or truncating, intended only for types that emulate ints but not other
numeric types:
And this was the new bit I didn't know about.
import operator
print operator.index(myobject)
But I did try
>>> import operator as op
>>> help(op.index)
Help on built-in function index in module operator:
index(...)
index(a) -- Same as a.__index__()
Which was no help at all, so I tried
>>> help(a.__index__)
Traceback (most recent call last):
File "<input>", line 1, in <module>
NameError: name 'a' is not defined
Which was what I expected!
So now with your input I can try:
>>> help(int.__index__)
Help on wrapper_descriptor:
__index__(...)
x[y:z] <==> x[y.__index__():z.__index__()]
Bingo! Although still doesn't anything explicitly about the need for an
integer!
But that was harder than it should have been! :-(
Thanks guys,
--
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
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