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Re: Recursive class | can you modify self directly?

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On 07/09/2013 03:01 PM, Russel Walker wrote:
>
> This is a simplified example of what I want to do:
>
>
> # THIS DOESN'T WORK
> from random import choice
>
> class Expr(object):
>      """
>      Expr(expr, op, val) -> an expression object.
>      """
>
>      def __init__(self, expr, op='', val=''):
>          self.expr = expr # can be another instance of Expression.
>          self.op = op
>          self.val = val
>
>      def __str__(self):
>          return ("%s %s %s" % (self.expr, self.op, self.val)).strip()
>
>      def expand(self):
>          self = Expr(self, choice('+-*/'), choice('12345'))

`self` is just a name.  In `expand()` you are rebinding the name `self` away from the object and to a new Expr instance. 
  If you want to change `self` the original object you have to do something like:

     def expand(self):
         self.op = choice('+-*/')
         self.val = choice('12345')

--
~Ethan~

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Recursive class | can you modify self directly? Russel Walker <russ.pobox@gmail.com> - 2013-07-09 15:01 -0700
  Re: Recursive class | can you modify self directly? Ian Kelly <ian.g.kelly@gmail.com> - 2013-07-09 16:18 -0600
  Re: Recursive class | can you modify self directly? Ian Kelly <ian.g.kelly@gmail.com> - 2013-07-09 16:20 -0600
    Re: Recursive class | can you modify self directly? Russel Walker <russ.pobox@gmail.com> - 2013-07-10 02:00 -0700
  Re: Recursive class | can you modify self directly? Dave Angel <davea@davea.name> - 2013-07-09 18:30 -0400
  Re: Recursive class | can you modify self directly? Ethan Furman <ethan@stoneleaf.us> - 2013-07-09 15:19 -0700
  Re: Recursive class | can you modify self directly? Russel Walker <russ.pobox@gmail.com> - 2013-07-10 01:58 -0700
    Re: Recursive class | can you modify self directly? Terry Reedy <tjreedy@udel.edu> - 2013-07-10 15:33 -0400
      Re: Recursive class | can you modify self directly? Russel Walker <russ.pobox@gmail.com> - 2013-07-10 13:09 -0700
  Re: Recursive class | can you modify self directly? Russel Walker <russ.pobox@gmail.com> - 2013-07-10 15:50 -0700
    Re: Recursive class | can you modify self directly? Ian Kelly <ian.g.kelly@gmail.com> - 2013-07-10 17:39 -0600

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