new.instancemethod __iter__

Steve Holden steve at holdenweb.com
Sun Feb 7 13:49:13 CET 2010


Martin Drautzburg wrote:
> Steven D'Aprano wrote:
> 
>> If you want iterator operations "similar to itertools", why does this
>> mean you need to replace anything? Just create your own iterators.
>>
>> Or use pre-processing and post-processing to get what you want.
>>
>> Can you show an example of what you would like to happen?
> 
> Steven, 
> 
> my classes repesent musical objects. The fundamental paradigm I want to
> apply is that of a Sequence, i.e. the most abstract aspect of music is
> that "things" occur in a certain order.
> 
> Then I have a TimedSequence class, which is a Sequences whose elements
> have a "time" attribute. I now want to be able to append such Sequences
> by writing
> 
> s1 = TimedSequence (time=1,'a') # one-element Sequence
> s2 = TimedSequence (time=2,'b')
> 
> y = s1*2 + s2
> 
> Naively appending those sequences would give me
> Time=1,'a'
> Time=1,'a'
> Time=2,'b'
> 
> but this is not what I want. Time needs to progress if I append a
> sequence to another. So what I really want is something like
> 
> Time=1,'a'
> Time=2,'a'
> Time=3,'b'
> 
> This implies that time is shifted to the next integer, but this is not
> always the case. I need to know about some kind of "alignment". In
> music this translates to "let a sequence start at the beginning of a
> bar", or half bar or quarter note or whatever.
> 
> So I want to write
> 
> y = s1*2 + s2(align=10)
> 
> which should iterate as
> 
> Time=1,'a'
> Time=2,'a'
> Time=10,'b'
> 
> I have no difficulty passing "align" to the object (using __call__) and
> use it while I furnish my own __iter__() method. However I don't quite
> see how I can do this with bare itertools, though I may be wrong here.
> 
> Bare in mind that it is not only about somehow getting the job done. The
> beauty of the resulting syntax is also important.
> 
In that case why not just assume that the timing of a sequence is
relative to the current time unless the "align" argument is given?

You might also need an event of zero duration to set the start time for
a sequence.

regards
 Steve
-- 
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