[Python-Dev] Lazy unpacking for struct module

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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