[Tutor] class initialization with a lot of parameters

[C.T. Matsumoto]

Hello Alan,

I see a new way to look at this design so I'm pretty excited to refactor the
code.
I've also been looking for an example to use 'overloading operators' as the
Learn
Python book calls it.

I think its time to close this discussion because the parameters question
has gotten
much advice, and this discussion seems to changing to objectness.

Thanks,

T

On Wed, Nov 11, 2009 at 7:19 PM, Alan Gauld <alan.gauld at btinternet.com>wrote:

>
> "C.T. Matsumoto" <c.t.matsumoto at gmail.com> wrote
>
>  The Table object you described I find more complicated if each table
>> stands
>> on its own it is decoupled from its compare partner. I suppose a function
>> that pairs the tables, feeding a Table object to its partner Table.compare
>> method.
>>
>
> Kind of.
>
> Think about something simpler. Like numbers.
>
> when we do
>
> if number1 == number2:
>
> what we actually do in Python is
>
> if number1.__eq__(number2):
>
>
> In other words we call the special method __eq__() of number1 passing
> in number2.
>
> So == is actually a method of the object on the left hand side.
>
> Similarly if you want to compare tables for equality you can define a class
> Table and provide an __eq__() method and you will be able to write
>
> if table1 == table2
>
> and it will work.
>
> And your __eq__() method can be a completely bespoke algorithm for
> determining what equality means for your table class. It could mean that
> every value of every field is the same or it could mean that the 3rd field
> in number1 is twice the value of the 5th field in number2. Its entirely up
> to you.
> But the ability to compare two things of the same class is an operation
> of the class.
>
> The same applies to >, <, >=, <= etc. They all have special methods
> that you can override to make object comparisons work the way you
> want them to.
>
>
>  Hmm ... This has got to sink in.
>>
>
> Its quite a big jump from traditional programming but one of the areas
> where OOP can dramatically simplify your code.  Once you build the
> objects to act like the built in types your code that uses those objects
> suddenly becomes much more readable
>
>
> --
> Alan Gauld
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
>
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-- 
Todd Matsumoto
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