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* PLPython and named arguments
@ 2016-10-04 12:20 Andrey Avakimov <aquarius1993@rambler.ru>
2016-10-04 12:37 ` Re: PLPython and named arguments Tom Lane <tgl@sss.pgh.pa.us>
2016-10-04 13:19 ` Re: PLPython and named arguments Adrian Klaver <adrian.klaver@aklaver.com>
0 siblings, 2 replies; 4+ messages in thread
From: Andrey Avakimov @ 2016-10-04 12:20 UTC (permalink / raw)
To: pgsql-sql
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 assignment
This can be solved by using such code:
arg_from, arg_to = 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
^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: PLPython and named arguments
2016-10-04 12:20 PLPython and named arguments Andrey Avakimov <aquarius1993@rambler.ru>
@ 2016-10-04 12:37 ` Tom Lane <tgl@sss.pgh.pa.us>
1 sibling, 0 replies; 4+ messages in thread
From: Tom Lane @ 2016-10-04 12:37 UTC (permalink / raw)
To: Andrey Avakimov <aquarius1993@rambler.ru>; +Cc: pgsql-sql
"Andrey Avakimov" <aquarius1993@rambler.ru> writes:
> 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 assignment
Let's see an example?
regards, tom lane
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^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: PLPython and named arguments
2016-10-04 12:20 PLPython and named arguments Andrey Avakimov <aquarius1993@rambler.ru>
@ 2016-10-04 13:19 ` Adrian Klaver <adrian.klaver@aklaver.com>
2016-10-04 13:36 ` Re: PLPython and named arguments Andrey Avakimov <aquarius1993@rambler.ru>
1 sibling, 1 reply; 4+ messages in thread
From: Adrian Klaver @ 2016-10-04 13:19 UTC (permalink / raw)
To: Andrey Avakimov <aquarius1993@rambler.ru>; pgsql-sql
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 assignment
Because of this?:
https://www.postgresql.org/docs/9.6/static/plpython-funcs.html
"
The arguments are set as global variables. Because of the scoping rules
of Python, this has the subtle consequence that an argument variable
cannot be reassigned inside the function to the value of an expression
that involves the variable name itself, unless the variable is
redeclared as global in the block. For example, the following won't work:
CREATE FUNCTION pystrip(x text)
RETURNS text
AS $$
x = x.strip() # error
return x
$$ LANGUAGE plpythonu;
because assigning to x makes x a local variable for the entire block,
and so the x on the right-hand side of the assignment refers to a
not-yet-assigned local variable x, not the PL/Python function parameter.
Using the global statement, this can be made to work:
CREATE FUNCTION pystrip(x text)
RETURNS text
AS $$
global x
x = x.strip() # ok now
return x
$$ LANGUAGE plpythonu;
But it is advisable not to rely on this implementation detail of
PL/Python. It is better to treat the function parameters as read-only."
So:
test=# select * from pystrip('test ');
ERROR: UnboundLocalError: local variable 'x' referenced before assignment
CONTEXT: Traceback (most recent call last):
PL/Python function "pystrip", line 2, in <module>
x = x.strip() # error
PL/Python function "pystrip"
>
> This can be solved by using such code:
>
> arg_from, arg_to = 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
>
--
Adrian Klaver
adrian.klaver@aklaver.com
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^ permalink raw reply [nested|flat] 4+ messages in thread
* Re: PLPython and named arguments
2016-10-04 12:20 PLPython and named arguments Andrey Avakimov <aquarius1993@rambler.ru>
2016-10-04 13:19 ` Re: PLPython and named arguments Adrian Klaver <adrian.klaver@aklaver.com>
@ 2016-10-04 13:36 ` Andrey Avakimov <aquarius1993@rambler.ru>
0 siblings, 0 replies; 4+ messages in thread
From: Andrey Avakimov @ 2016-10-04 13:36 UTC (permalink / raw)
To: Adrian Klaver <adrian.klaver@aklaver.com>; +Cc: pgsql-sql
OMG... I feel ashamed that I missed that part of the documentation.
Thank you
Best Regards,
Andrew
> 04.10.2016, 16:22:55 пользователь Adrian Klaver (adrian.klaver@aklaver.com) написал:
>
> 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 assignment
>
> Because of this?:
>
> https://www.postgresql.org/docs/9.6/static/plpython-funcs.html
> "
> The arguments are set as global variables. Because of the scoping rules
> of Python, this has the subtle consequence that an argument variable
> cannot be reassigned inside the function to the value of an expression
> that involves the variable name itself, unless the variable is
> redeclared as global in the block. For example, the following won't work:
>
> CREATE FUNCTION pystrip(x text)
> RETURNS text
> AS $$
> x = x.strip() # error
> return x
> $$ LANGUAGE plpythonu;
>
> because assigning to x makes x a local variable for the entire block,
> and so the x on the right-hand side of the assignment refers to a
> not-yet-assigned local variable x, not the PL/Python function parameter.
> Using the global statement, this can be made to work:
>
> CREATE FUNCTION pystrip(x text)
> RETURNS text
> AS $$
> global x
> x = x.strip() # ok now
> return x
> $$ LANGUAGE plpythonu;
>
> But it is advisable not to rely on this implementation detail of
> PL/Python. It is better to treat the function parameters as read-only."
>
> So:
>
> test=# select * from pystrip('test ');
> ERROR: UnboundLocalError: local variable 'x' referenced before assignment
> CONTEXT: Traceback (most recent call last):
> PL/Python function "pystrip", line 2, in <module>
> x = x.strip() # error
> PL/Python function "pystrip"
>
> >
> > This can be solved by using such code:
> >
> > arg_from, arg_to = 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
> >
>
> --
> Adrian Klaver
> adrian.klaver@aklaver.com
>
> --
> Sent via pgsql-sql mailing list (pgsql-sql@postgresql.org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-sql
>
>
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2016-10-04 12:20 PLPython and named arguments Andrey Avakimov <aquarius1993@rambler.ru>
2016-10-04 12:37 ` Tom Lane <tgl@sss.pgh.pa.us>
2016-10-04 13:19 ` Adrian Klaver <adrian.klaver@aklaver.com>
2016-10-04 13:36 ` Andrey Avakimov <aquarius1993@rambler.ru>
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