[Python-Dev] Lazy unpacking for struct module (original) (raw)

Lukas Lueg lukas.lueg at googlemail.com
Fri Jun 17 16:44:12 CEST 2011

The followup: I've implemented a new StructView-object for 3.3a-trunk. The object takes and existing Struct-object and provides on-access unpacking. The breaking point where this object is faster than calling Struct.unpack seems to be somewhere around 12 fields in the format-string. Format strings with less fields expose too much overhead of entering the C-code and staying there a little longer to unpack all fields is actually faster.

Having fifteen or more fields in a format-string seems unlikely and I'll therefor abandon the idea of providing this mechanism.

2011/6/14 Lukas Lueg <lukas.lueg at googlemail.com>:

So I really can't see what harm it could do, except for maybe a tiny performance reduction in the case where you extract all the fields, or refer to extracted fields repeatedly. Referring to the view-object multiple times should not be a problem since the object can create and hold references to the unpacked values it created; remember that they are all immutable.

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