Re: Pyro 4.20 serpent serializer issues

List Readers:

You can switch serializers by setting the environment variable
Linux:
export PYRO_SERIALIZER=pickle
Windows:
set PYRO_SERIALIZER=pickle

Irmen:

The documentation page at
http://pythonhosted.org/Pyro4/api/config.htmlrefers back to itself.  I
think that you intended for it to refer to:
http://pythonhosted.org/Pyro4/config.html#overview-of-config-items
which is where I (finally) found the answer I needed.

May I suggest putting information on _how_ to change serializers earlier in
the documentation?  It took me an age to find out how to switch back to
pickle. (My code already has a work-around for a pickle idiosyncrasy, and I
suspect that I will have to vastly expand that to handle decimal and
datetime instances (if I even can) to support serpent.  I am doing SQL
database I/O, and do not know in advance what type of data my user might
throw at me.
--
Vernon



On Tue, Jun 11, 2013 at 8:25 PM, Irmen de Jong <[email protected]> wrote:

> On 11-6-2013 15:01, Éric Piel wrote:
> > On 09/06/13 01:38, Irmen de Jong wrote:
> > :
> >> Decimals are encoded as a literal string (because otherwise you will
> lose precision).
> >> The receiver however needs to 'know' this and will have to convert the
> string back to a
> >> decimal.Decimal. Similarly, datetime.datetime are encoded as a ISO
> formatted date+time
> >> string, and the receiver will have to convert it back explicitly (if
> desired).
> > :
> >> The key issue here is that when not using pickle, you probably will
> have to redesign
> >> your remote method contracts if they depend a lot on custom types on
> both ends. If you
> >> stick to Python literals mainly, the pain will be a lot less or even
> non-existent...
> >
> > Hi Irmen,
> > Just to be sure I understand correctly, does this mean that in Pyro 4.20
> > (with the default serializer), a method returning a decimal.Decimal will
> > return a string when called remotely via Pyro?
>
> Yep, that's right.
> The string form makes sure no precision is lost. You can convert it back
> to a Decimal if
> you need (but yeah, that will have to be an explicit step in your code).
>
> The new serializer (serpent), and the json one even more so, trade
> expressive power for
> security (and human readability, if that matters). You gain some, you
> loose some.
>
> You can check it out by enabling LOGWIRE and then looking in the log to
> see what Pyro
> puts on the wire. Or if you're interested in serpent specifically, you can
> check it out
> directly by playing with serpent.dumps().
>
> If you don't like the way serpent serializes certain types, you can
> register your own
> custom hooks (Pyro already does this, for a few types). Example:
>
> >>> import serpent
> >>> def serialize_decimal(obj, serializer, stream, indent):
> ...   serializer._serialize("decimal.Decimal('%s')" % obj, stream, indent)
> ...
> >>> serpent.register_class(decimal.Decimal, serialize_decimal)
> >>> print serpent.dumps(decimal.Decimal("1234.56789"))
> # serpent utf-8 python3.2
> "decimal.Decimal('1234.56789')"
> >>>
>
> Ofcourse, this specific example can no longer be deserialized by serpent
> itself: the
> serialized data is no longer a python literal expression.
>
> For security reasons (again), Pyro only converts a limited set of well
> known types back
> into actual objects of that type. It is not possible (yet?) to extend that
> mechanism.
> (This doesn't apply to pickle)
>
> If you find that you loose to much expressive power by using serpent or
> one of the other
> serializers, you can always switch back to pickle. But you'll then have to
> deal with its
> security problems.
>
> Cheers
> Irmen
>
>
>
>
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