cPickle problem

[Vojin Jovanovic]

Thanks, I understand this a bit better.  I changed my implementation of foo
like this

>>> class foo:
 def __init__(self):
  self.y=4
  self.e={'a':'self.y',
   'b':'self.a+4'}
 def __getattr__(self,arg):
  if self.e.has_key(arg) == 0:
   raise AttributeError,  "foo instance has no attribute '" + arg + "'"
  try:
   exec 'result =' + self.e[arg]
   return result
  except:
   return '#U'
 def addequation(self,attr,value):
  self.e[attr] = value


>>> k=foo()
>>> k.e
{'b': 'self.a+4', 'a': 'self.y'}
>>> k.a
4
>>> k.b
8

>>> k.ddd
Traceback (most recent call last):
  File "<pyshell#121>", line 1, in ?
    k.ddd
  File "<pyshell#105>", line 8, in __getattr__
    raise AttributeError,  "foo instance has no attribute '" + arg + "'"
AttributeError: foo instance has no attribute 'ddd'

As you can see I added a new method 'addequation' that works like this

>>> k.addequation('c','self.a+self.b')
>>> k.e
{'b': 'self.a+4', 'c': 'self.a+self.b', 'a': 'self.y'}
>>> k.c
12

and now I have another question.

can I replace addequation with __setattr__ so that I can type

>>>k.c='self.a+self.b'

to achieve the same effect.
>>> k.e
{'b': 'self.a+4', 'c': 'self.a+self.b', 'a': 'self.y'}
>>> k.c
12

My attempts with __setattr__ were unsuccessful.

Thanks for you help

Vin