On Wed, Apr 15, 2009 at 12:27 PM, Carnell, James E <
jecarn...@saintfrancis.com> wrote:
> Since # the list seems thick with OOP questions at the moment, I thought
> this might # be relevant. Digest and enjoy.
>
> class Item ( object ):
>
> def __init__( self ):
> self._FullName = ''
> self._Recovery = 0
> self._Exporter = SimpleItemExporter (); # <----? Don't
> understand
>
> Bummer, I was hoping to consider myself at the tip of intermediate
> python programming <sigh>...
>
> This is the first time I have ever seen a variable set to what appears
> to be a function address(?). Since I am at work I can't copy paste this
> thing yet. Is SimpleItemExporter from the parent class, object? I am
> assuming Item extends or inherits (or whatever the right "word" is) from
> object.
First off, the semicolon is probably a syntax error.
SimpleItemExporter is probably a class, but I don't think object is the
parent. If you were trying to access something from object I'm fairly
certain you'd use the dot operator, so it would be
object.SimpleItemExporter()
But if it's a class it would be a new instance of that class. Otherwise it
doesn't make a lot of sense to have the parenthesis (unless
SimpleItemExporter returns something useful... which it isn't named like it
should).
Consider the following:
In [1]: def foo():
...: print "Hello"
...:
...:
In [2]: x = foo()
Hello
In [3]: x
In [4]: x('a')
---------------------------------------------------------------------------
TypeError Traceback (most recent call last)
/home/wayne/<ipython console> in <module>()
TypeError: 'NoneType' object is not callable
In [5]: class foo:
...: def __init__(self, spam):
...: print spam
...:
...:
In [7]: x = foo('eggs')
eggs
In [8]: x
Out[8]: <__main__.foo instance at 0x9f0304c>
In [9]: x()
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
/home/wayne/<ipython console> in <module>()
AttributeError: foo instance has no __call__ method
In [10]: x.__init__('eggs')
eggs
--and---
In [11]: class spam:
....: def __init__(self, eggs):
....: lay(eggs)
....: def lay(x):
....: print x
....:
....:
In [13]: class foo(spam):
....: def __init__(self, bar):
....: lay(bar)
....:
....:
In [14]: x = foo('Ni')
---------------------------------------------------------------------------
NameError Traceback (most recent call last)
/home/wayne/<ipython console> in <module>()
/home/wayne/<ipython console> in __init__(self, bar)
NameError: global name 'lay' is not defined
---------------------
The above snippets seem to show what I stated before - SimpleItemExporter is
a class on it's own - not a method/function in the object class. If that
were the case then my class foo should have direct access to the lay
function, AFAIK.
HTH,
Wayne
_______________________________________________
Tutor maillist - Tutor@python.org
http://mail.python.org/mailman/listinfo/tutor
