lots of similar classes?

Hans Nowak wurmy at earthlink.net
Mon Jan 20 18:14:41 CET 2003


boncelet wrote:
> I want to create lots of similar classes and wonder what's the
> best/most efficient way.
> 
> Pseudo-code looks like this:
> 
> class Super:
>   def __init__(self,name,lots_of_other_arguments):
>     self.name=name
>     <<set rest of arguments, etc>>
> 
> class A(Super):
>   def __init__(self,name='a',lots_of_other_arguments):
>     Super.__init__(self,name,lots_of_other_arguments)
> 
> There will be lots of these, eg., A, B, C etc. Most of these will
> differ only in the name argument.  In a few, I might want to use only
> a subset of the "other arguments".
> 
> My problem is rewriting the "lot_of_other_arguments" over and over
> again seems wasteful, error-prone, and fragile.  Is there a better
> way?

To take a page from Martin Fowler's book, lots of arguments for a method is a 
"code smell".  Consider writing a separate class for this.  I regularly use a 
variant of the following, especially when command line options translate to 
options in a class:

class Options:
     def __init__(self):
         self.foo = ""
         self.bar = None
         # ...etc...

options = Options()

# set some options
options.baz = "bletch"

class MyClass:
     def __init__(self, name, options):
         self.options = options

myclass = MyClass("foo", options)

Now, your class uses an instance of Options to hold all these variables, rather 
than having them in its own namespace.  Much easier to pass around.

HTH,

-- 
Hans (base64.decodestring('d3VybXlAZWFydGhsaW5rLm5ldA=='))
# decode for email address ;-)
The Pythonic Quarter:: http://www.awaretek.com/nowak/
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