[Python-ideas] Revised**5 PEP on yield-from

Greg Ewing greg.ewing at canterbury.ac.nz
Sun Mar 1 23:32:21 CET 2009

Jacob Holm wrote:
> Arnaud Delobelle wrote:
>> * What you are measuring the time complexity of.
> The time for a single 'next', 'send', 'throw' or 'close' call to a 
> generator or a single "yield from" expression,

How are you measuring 'time', though? Usually when discussing
time complexities we're talking about the number of some
fundamental operation being performed, and assuming that
all such operations take the same time. What operations
are you counting here?

> One interesting thing to note is that all non-contrived examples
 > I have seen only build simple chains of iterators, and only do
 > that by adding one at a time in the deepest nested one. This is
 > the best possible case for my algorithm. If you stick to that,
 > the time per operation is O(1).

I don't understand that limitation. If you keep a stack of
active generators, you always have constant-time access to the
one to be resumed next. There's some overhead for pushing and
popping the stack, but it follows exactly the same pattern
as the recursive calls you'd be making if you weren't using
some kind of yield-from, so it's irrelevant when comparing the


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