[Python-Dev] slice subscripts for sequences and mappings (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Sat Mar 3 13:48:53 CET 2012

Le samedi 03 mars 2012 à 14:41 +0200, Eli Bendersky a écrit :

>> I'd expect slice subscripts to be part of the sequence interface, and >> yet they are not. In fact, they are part of the mapping interface. For >> example, the list object has its slice get/set methods assigned to a >> PyMappingMethods struct. So does a bytes object, and pretty much every >> other object that wants to support subscripts. > > It comes from: > http://hg.python.org/cpython/rev/245224d1b8c9 > http://bugs.python.org/issue400998 > > Written by Michael Hudson and reviewed by Guido. > I wonder why this patch chose to add mapping protocol support to tuples > and lists, rather than add a tp slot for extended slicing. >

Why a separate tp slot for extended slicing? ISTM slicing pertains to sequences, similarly to other numeric indices. If you look at PySequenceMethods it has these (apparently no longer used fields):

Yes, I meant sq_ slot, my bad.

Regards

Antoine.

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