[Tutor] Another Question

[Michael P. Reilly]

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> Sorry, I have so many question. Here is another one:
> 
> class A:
>     def fun(self, *options):
>         ... # some codes here
> 
> class B(A):
>     def fun(self, *options):
>         ...# some codes here
>         ...# I need to call fun in class A here
> 
> How can the method fun in class B use its option tuple to call the fun=
>  method in the class A?
> The problem is caused because we can change the tuple (options).

Here is where the apply function comes in handy.  A Python function's
arguments are broken into two parts: positional (tuple) and named
(dictionary).  The apply function allows you to pass either or both
types to a function:

>>> def spam(*options, **keywords):
...   print options, keywords
...
>>> spam(1, 2, 3, name='Arcege')
(1, 2, 3) {'name': 'Arcege'}
>>> spam(1, 2, 3)
(1, 2, 3) {}
>>> spam(name='Arcege')
() {'name': 'Arcege'}
>>> apply(spam, (1, 2, 3), {'name': 'Arcege'})
(1, 2, 3) {'name': 'Arcege'}
>>> apply(spam, (1, 2, 3))
(1, 2, 3) {}

Python 2.0 also has a new syntax to use instead of apply:
>>> spam(*(1,2,3), **{'name': 'Arcege'})
(1, 2, 3) {'name': 'Arcege'}
>>> 

So in your example, the B.fun method could call:

class B(A):
  def fun(self, *options):
    if sys.version[:3] == '2.0':
      A.fun( *( (self,) + options ) )
    else:
      apply( A.fun, (self,) + options )

Don't forget to include self as the first argument when calling unbound
methods.

  -Arcege

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| Michael P. Reilly, Release Manager  | Email: arcege@shore.net        |
| Salem, Mass. USA  01970             |                                |
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