[Patches] [ python-Patches-1181334 ] range() in for loops, again

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Patches item #1181334, was opened at 2005-04-12 09:00
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Category: Core (C code)
Group: None
Status: Open
Resolution: None
Priority: 5
Submitted By: Armin Rigo (arigo)
Assigned to: Nobody/Anonymous (nobody)
Summary: range() in for loops, again

Initial Comment:
Here is (yet) a(nother) patch to make range() lazy and fast in the context of for loops.

This implementation allows any built-in function or method to declare two C implementations if it wants to.  The second implementation, if present, is used when the caller can know for sure that it will only ever need an iterator over the result.  This is done with a new ml_flag_iter member of PyMethodDef.  To minimize compatibility issues a new METH_ITERABLE flag must be set when ml_flag_iter is valid.

The CALL_FUNCTION bytecode uses that if the immediately following bytecode is GET_ITER.

The patch updates range() to use this flag and build an xrange iterator object.

Of course the same technique could be applied to other built-in functions, but none spring to mind.  Maybe a simple patch that only special-cases range() would do just as well...

FWIW, I get a 5% speed-up on pystone with this patch.

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