REPOST: Re: odd problem, most likely stupid one too :-)

[Tim Roberts]

Dave Harrison <dlharris at mail.usyd.edu.au> wrote:

>Ive written a class named packet, and I have a list on 
>values that I am using to create my packets by passing
>the values in as I instantiate the classes I am creating.
>
>I do the creation in a for loop,
>
>for item in itemlist:
>	PACKET = Packet(item)
>	paclist.append(PACKET)
>
>except that when I try to go back through and see the 
>packets in my paclist they are all exactly the same as
>the final one that I store in the list. As in I do,
>
>for pac in paclist:
>	print pac.getVal()
>
>and I get exactly the same value, despite the fact that
>I know for sure they are different.

This might happen if, for example, you were storing the packets in a class
variable or a global variable instead of an instance variable.  This class,
for example, would behave exactly as you describe:

  class Packet:
      value = Null

      def __init__(self,pkt):
          value = pkt

      def getVal(self):
          return self.value

The solution is to skip the class global:

  class Packet:
      def __init__(self,pkt):
          self.value = pkt

      def getVal(self):
          return self.value
--
- Tim Roberts, timr at probo.com
  Providenza & Boekelheide, Inc.

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From: Tim Roberts <timr at probo.com>
Newsgroups: comp.lang.python
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