From: "Andrey Avakimov" <aquarius1993@rambler.ru>
To: "Adrian Klaver" <adrian.klaver@aklaver.com>
Cc: "Pgsql Sql" <pgsql-sql@postgresql.org>
Reply-To: "Andrey Avakimov" <aquarius1993@rambler.ru>
Subject: Re: PLPython and named arguments
Date: Tue, 4 Oct 2016 16:36:59 +0300
Content-Disposition: inline
Content-Transfer-Encoding: quoted-printable
Content-Type: text/plain; charset="utf-8"; format="flowed"
In-Reply-To: <ff3905f6-1954-973c-8314-6a3645299446@aklaver.com>
Message-Id: <1475588219.350324.21966.19771@mail.rambler.ru>
MIME-Version: 1.0
References: <ff3905f6-1954-973c-8314-6a3645299446@aklaver.com>
Precedence: bulk
Sender: pgsql-sql-owner@postgresql.org


OMG... I feel ashamed that I missed that part of the documentation.
Thank you

Best Regards,
Andrew

> 04.10.2016, 16:22:55 =D0=BF=D0=BE=D0=BB=D1=8C=D0=B7=D0=BE=D0=B2=D0=B0=D1=
=82=D0=B5=D0=BB=D1=8C Adrian Klaver (adrian.klaver@aklaver.com) =D0=BD=D0=
=B0=D0=BF=D0=B8=D1=81=D0=B0=D0=BB:
>=20
> On 10/04/2016 05:20 AM, Andrey Avakimov wrote:
> > Hello
> >
> > My question is about plpython behavior. In some cases procedure ignores
> > named arguments and raises an error like:
> >
> > UnboundLocalError: local variable 'arg_from' referenced before assignme=
nt
>=20
> Because of this?:
>=20
> https://www.postgresql.org/docs/9.6/static/plpython-funcs.html
> "
> The arguments are set as global variables. Because of the scoping rules=20
> of Python, this has the subtle consequence that an argument variable=20
> cannot be reassigned inside the function to the value of an expression=20
> that involves the variable name itself, unless the variable is=20
> redeclared as global in the block. For example, the following won't work:
>=20
> CREATE FUNCTION pystrip(x text)
>    =C2=A0=C2=A0=C2=A0RETURNS text
> AS $$
>    =C2=A0=C2=A0=C2=A0x =3D x.strip()  =C2=A0=C2=A0# error
>    =C2=A0=C2=A0=C2=A0return x
> $$ LANGUAGE plpythonu;
>=20
> because assigning to x makes x a local variable for the entire block,=20
> and so the x on the right-hand side of the assignment refers to a=20
> not-yet-assigned local variable x, not the PL/Python function parameter.=
=20
> Using the global statement, this can be made to work:
>=20
> CREATE FUNCTION pystrip(x text)
>    =C2=A0=C2=A0=C2=A0RETURNS text
> AS $$
>    =C2=A0=C2=A0=C2=A0global x
>    =C2=A0=C2=A0=C2=A0x =3D x.strip()  =C2=A0=C2=A0# ok now
>    =C2=A0=C2=A0=C2=A0return x
> $$ LANGUAGE plpythonu;
>=20
> But it is advisable not to rely on this implementation detail of=20
> PL/Python. It is better to treat the function parameters as read-only."
>=20
> So:
>=20
> test=3D# select * from pystrip('test  =C2=A0=C2=A0');
> ERROR:  =C2=A0=C2=A0UnboundLocalError: local variable 'x' referenced befo=
re assignment
> CONTEXT:  =C2=A0=C2=A0Traceback (most recent call last):
>    =C2=A0=C2=A0=C2=A0PL/Python function "pystrip", line 2, in <module>
>      =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0x =3D x.strip()  =C2=A0=C2=A0# error
> PL/Python function "pystrip"
>=20
> >
> > This can be solved by using such code:
> >
> > arg_from, arg_to =3D args
> >
> > But the reasons of such behavior are still unclear.
> >
> > Does anyone faced this thing?
> >
> > I will gladly provide any further information if needed.
> >
> > Best Regards,
> > Andrew
> >
>=20
> --=20
> Adrian Klaver
> adrian.klaver@aklaver.com
>=20
> --=20
> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-sql
>=20
>=20

--=20
Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-sql