[Tutor] Class Inheritance -> NameError

[Liam Clarke-Hutchinson]

Hi Tim, 

Either - 

class test:
    def __init__(self,v):
        self.__val = v
    def val(self):
        print self.__val


class sub(test):
    def __init__(self, v):
        test.__init__(v)
        self.val()

or - 

class sub(test):
    def __init__(self, v):
        test.__init__(v)
        test.val()




That will resolve your calling the method problem, but self.__val won't
inherit (I think). I don't recommend using double underscored variables
unless there's a really good reason, C# et al be damned.

Oh, and if self.__val / val is set by the superclasses __init__ method, then
you'll need to call it specifically, or otherwise you'll get a
UnboundLocalError, because self.__val/val won't exist.



Liam Clarke-Hutchinson

-----Original Message-----
From: tutor-bounces at python.org [mailto:tutor-bounces at python.org] On Behalf
Of Tim Johnson
Sent: Thursday, 1 December 2005 3:46 p.m.
To: tutor at python.org
Subject: [Tutor] Class Inheritance -> NameError


The following code snippet is meant to test inheritance:
class test:
    def __init__(self,v):
        self.__val = v
    def val(self):
        print self.__val
class sub(test):
    def __init__(self):
        val()
The following console session has an error:
>>> T = mylib.test('hello')
>>> s = mylib.sub()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "mylib.py", line 1612, in __init__
    val()
NameError: global name 'val' is not defined

## what do I need to do to make the 'test method visible
## class 'sub?
thanks
tim

-- 
Tim Johnson <tim at johnsons-web.com>
      http://www.alaska-internet-solutions.com
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