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Groups > comp.lang.python > #15912

Re: Dynamically Generate Methods

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On Fri, Nov 18, 2011 at 7:51 AM, GZ <zyzhu2000@gmail.com> wrote:
> Hi,
>
> I have a class Record and a list key_attrs that specifies the names of
> all attributes that correspond to a primary key.
>
> I can write a function like this to get the primary key:
>
> def get_key(instance_of_record):
>   return tuple(instance_of_record.__dict__[k] for k in key_attrs)
>
> However, since key_attrs are determined at the beginning of the
> program while get_key() will be called over and over again, I am
> wondering if there is a way to dynamically generate a get_ley method
> with the key attributes expanded to avoid the list comprehension/
> generator.

(Accidentally sent this to the OP only)

This is exactly what the attrgetter factory function produces.

from operator import attrgetter
get_key = attrgetter(*key_attrs)

But if your attribute names are variable and arbitrary, I strongly
recommend you store them in a dict instead.  Setting them as instance
attributes risks that they might conflict with the regular attributes
and methods on your objects.

Cheers,
Ian

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Dynamically Generate Methods GZ <zyzhu2000@gmail.com> - 2011-11-18 06:51 -0800
  Re: Dynamically Generate Methods Jean-Michel Pichavant <jeanmichel@sequans.com> - 2011-11-18 17:56 +0100
  Re: Dynamically Generate Methods Duncan Booth <duncan.booth@invalid.invalid> - 2011-11-18 17:52 +0000
  Re: Dynamically Generate Methods Ian Kelly <ian.g.kelly@gmail.com> - 2011-11-18 11:04 -0700
    Re: Dynamically Generate Methods GZ <zyzhu2000@gmail.com> - 2011-11-20 03:23 -0800

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