[Tutor] Challenge supporting custom deepcopy with inheritance

[W W]

On Mon, Jun 1, 2009 at 8:59 AM, Alan Gauld <alan.gauld at btinternet.com>wrote:

>
> "W W" <srilyk at gmail.com> wrote
>
>  ( Multiple constructors (or factory methods) is one feature I  would like
>>> to see added to Python! )
>>>
>>
>> Wouldn't it be possible to create sort of a... bastardization? i.e.
>>
>> def __init__(self, *args):
>>   if len(args) == 0:
>>       #do something
>>   if len(args) == 1:
>>      #do something else
>>
>> Or would that create more problems than is worth it?
>>
>
> Thats the standard workaround but its not clean and certainly
> not self documenting. Its also not reliable becaause thre is nothing
> to stop someone calling it with the first argument of the 2 arg case
> (a filename maybe?) and then it gets treated as a single arg case
> ( a tuple of values say?) Oops!
>
> Whereas in C++/Java style you could say
>
> class C:
>   @constructor
>   def C(fname, count);...
>
>   @constructor
>   def C(valueTuple):....
>
> etc.
>
> Or in Delphi style:
>
> class C:
>    @constructor
>    def LoadFromFile(fname, count): ...
>    @constructor
>    def Create(valueTuple):...
>
> Personally I prefer the Delphi style sincve it makes the constructor
> call explicit and adds to the documentation.
>
> Alan G
>

That does make it problematic... although I suppose checking the type would
be a workaround - still, not simple or beautiful. Has this been introduced
as a PEP?

-Wayne
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