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Date: Fri, 18 Nov 2011 17:56:29 +0100
From: Jean-Michel Pichavant <jeanmichel@sequans.com>
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To: GZ <zyzhu2000@gmail.com>
Subject: Re: Dynamically Generate Methods
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GZ 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.
>
> For example, if key_attrs=['A','B'], I want the generated function to
> be equivalent to the following:
>
> def get_key(instance_of_record):
>    return (instance_of_record['A'],instance_of_record['B'] )
>
> I realize I can use eval or exec to do this. But is there any other
> way to do this?
>
> Thanks,
> gz
>
>
>
>   
Hi,

you may want to do something like

class Record(object):
  PRIMARY_KEY = []
  def __init__(self):
    for key in self.PRIMARY_KEY:
      setattr(self, key, None)

  def getPrimaryKeyValues(self):
    return [ getattr(self, key) for key in self.PRIMARY_KEY]


class FruitRecord(Record):
  PRIMARY_KEY = ['fruit_id', 'fruit_name']



JM

PS : there's a high chance that a python module already exists to access 
your database with python objects.