[Python-Dev] proposal: core support for "fast" sequence iteration

[Greg Stein]

+1

coolness.


On Sat, Jun 17, 2000 at 05:44:58PM +0200, Fredrik Lundh wrote:
> mark wrote:
> 
> > Its a fair bit of code to duplicate everywhere you want the speed increase.
> > How can we add a similar scheme to the core, so the changes people need to
> > make are trivial (to the point where the change is zero!)?
> 
> okay, here's my current proposal:
> 
>     PyObject* PySequence_Fast(PyObject *o) 
> 
>         Return value: New reference. 
> 
>         Returns the o as a tuple or a list on success, and
>         NULL on failure.  If o doesn't have the right type,
>         it is converted to a tuple using PySequence_Tuple.
> 
>         This is equivalent to the following Python code:
> 
>             if type(o) in (ListType, TupleType):
>                 return o
>             return tuple(o)
> 
>         This function is intended to be used together with
>         PySequence_Fast_GET_ITEM, for functions that need
>         to loop over a read-only sequence as fast as they
>         possibly can, while still supporting any object that
>         implements the sequence protocol.
> 
>     PyObject* PySequence_Fast_GET_ITEM(PyObject *seq, int i)
> 
>         Return value: Borrowed reference. 
> 
>         Returns the object at position i, from the sequence
>         seq (which must be a list or a tuple).  This is a
>         macro, and has no error checking.
> 
>         If you need error checking, use PySequence_GetItem.
> 
> for the rationale, see my earlier posts in the "list.extend" thread.
> 
> unless somebody comes up with a more efficient solution, I'll wrap
> this up together with the list.extend patch (first thing tomorrow).
> 
> </F>
> 
> 
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-- 
Greg Stein, http://www.lyra.org/