Why less emphasis on private data?

[Gabriel Genellina]

Re: Why less emphasis on private data?

At Wednesday 10/1/2007 04:33, Hendrik van Rooyen wrote:

>Oh I am of the opposite conviction - Like the fellow of the Circuit Cellar
>I forget his name ( Steve Circia (?) ) who said: "My favourite Programming
>Language is Solder"..

Almost right: Steve Ciarcia.


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Gabriel Genellina
Softlab SRL






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[Steve Holden]

Re: Why less emphasis on private data?

Paul Boddie wrote:

Paul Rubin wrote:

>Right, the problem is if those methods start changing the "private"
>variable. I should have been more explicit about that.
>>
>class A:
> def __init__(self):
> self.__x = 3
> def foo(self):
> return self.__x
>>
>class B(A): pass
>>
>class A(B):
> def bar(self):
> self.__x = 5 # clobbers private variable of earlier class named A

>
Has this ever been reported as a bug in Python? I could imagine more
sophisticated "name mangling": something to do with the identity of the
class might be sufficient, although that would make the tolerated
"subversive " access to private attributes rather difficult.
>
Paul
>

It would also force the mangling to take place at run-time, which would
probably affect efficiently pretty adversely (thinks: should really
check that mangling is a static mechanism before posting this).

regards
Steve
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[Bart Ogryczak]

Re: Why less emphasis on private data?

On Jan 7, 1:07 am, "time.sw...@gma il.com" <time.sw...@gma il.com>
wrote:

Coming from a C++ / C# background, the lack of emphasis on private data
seems weird to me. I've often found wrapping private data useful to
prevent bugs and enforce error checking..
>
It appears to me (perhaps wrongly) that Python prefers to leave class
data public. What is the logic behind that choice?

Often it´s a question of efficiency. Function calls in Python are
bloody slow. There is no "inline" directive, since it´s intepreted,
not compiled. Eg. consider code like that:

class MyWhatever:
...
def getSomeAttr(sel f):
return self._someAttr
def getSomeOtherAtt r(self):
return self._someOther Attr

[x.getSomeAttr() for x in listOfMyWhateve rs if x.getSomeOtherA ttr() ==
'whatever']

You´d get it running hundreds times faster doing it the "wrong" way:

[x._someAttr for x in listOfMyWhateve rs if x._someOtherAtt r ==
'whatever']

[Paul Rubin]

Re: Why less emphasis on private data?

Steve Holden <steve@holdenwe b.comwrites:

class A(B):
def bar(self):
self.__x = 5 # clobbers private variable of earlier class named A

Has this ever been reported as a bug in Python? I could imagine more
sophisticated "name mangling": something to do with the identity of the
class might be sufficient, although that would make the tolerated
"subversive " access to private attributes rather difficult.

It would also force the mangling to take place at run-time, which
would probably affect efficiently pretty adversely (thinks: should
really check that mangling is a static mechanism before posting this).

I think it could still be done statically. For example, the mangling
could include a random number created at compile time when the class
definition is compiled, that would also get stored in the class object.

I guess there are other ways to create classes than class statements
and those would have to be addressed too.