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>PostgreSQL 8.1.9 Documentation</TH
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>Chapter 39. PL/Python - Python Procedural Language</H1
><DIV
CLASS="TOC"
><DL
><DT
><B
>Table of Contents</B
></DT
><DT
>39.1. <A
HREF="plpython.html#PLPYTHON-FUNCS"
>PL/Python Functions</A
></DT
><DT
>39.2. <A
HREF="plpython-trigger.html"
>Trigger Functions</A
></DT
><DT
>39.3. <A
HREF="plpython-database.html"
>Database Access</A
></DT
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><A
NAME="AEN36754"
></A
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NAME="AEN36756"
></A
><P
> The <SPAN
CLASS="APPLICATION"
>PL/Python</SPAN
> procedural language allows
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> functions to be written in the
<A
HREF="http://www.python.org"
TARGET="_top"
>Python language</A
>.
</P
><P
> To install PL/Python in a particular database, use
<TT
CLASS="LITERAL"
>createlang plpythonu <TT
CLASS="REPLACEABLE"
><I
>dbname</I
></TT
></TT
>.
</P
><DIV
CLASS="TIP"
><BLOCKQUOTE
CLASS="TIP"
><P
><B
>Tip: </B
> If a language is installed into <TT
CLASS="LITERAL"
>template1</TT
>, all subsequently
created databases will have the language installed automatically.
</P
></BLOCKQUOTE
></DIV
><P
> As of <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> 7.4, PL/Python is only
available as an <SPAN
CLASS="QUOTE"
>"untrusted"</SPAN
> language (meaning it does not
offer any way of restricting what users can do in it). It has
therefore been renamed to <TT
CLASS="LITERAL"
>plpythonu</TT
>. The trusted
variant <TT
CLASS="LITERAL"
>plpython</TT
> may become available again in future,
if a new secure execution mechanism is developed in Python.
</P
><DIV
CLASS="NOTE"
><BLOCKQUOTE
CLASS="NOTE"
><P
><B
>Note: </B
> Users of source packages must specially enable the build of
PL/Python during the installation process. (Refer to the
installation instructions for more information.) Users of binary
packages might find PL/Python in a separate subpackage.
</P
></BLOCKQUOTE
></DIV
><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="PLPYTHON-FUNCS"
>39.1. PL/Python Functions</A
></H1
><P
> Functions in PL/Python are declared via the usual <A
HREF="sql-createfunction.html"
><I
>CREATE FUNCTION</I
></A
>
syntax. For example:
</P><PRE
CLASS="PROGRAMLISTING"
>CREATE FUNCTION myfunc(text) RETURNS text
AS 'return args[0]'
LANGUAGE plpythonu;</PRE
><P>
The Python code that is given as the body of the function definition
gets transformed into a Python function.
For example, the above results in
</P><PRE
CLASS="PROGRAMLISTING"
>def __plpython_procedure_myfunc_23456():
return args[0]</PRE
><P>
assuming that 23456 is the OID assigned to the function by
<SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
>.
</P
><P
> If you do not provide a return value, Python returns the default
<TT
CLASS="SYMBOL"
>None</TT
>. <SPAN
CLASS="APPLICATION"
>PL/Python</SPAN
> translates
Python's <TT
CLASS="SYMBOL"
>None</TT
> into the SQL null
value.<A
NAME="AEN36786"
></A
>
</P
><P
> The <SPAN
CLASS="PRODUCTNAME"
>PostgreSQL</SPAN
> function parameters are available in
the global <TT
CLASS="VARNAME"
>args</TT
> list. In the
<CODE
CLASS="FUNCTION"
>myfunc</CODE
> example, <TT
CLASS="VARNAME"
>args[0]</TT
> contains
whatever was passed in as the text argument. For
<TT
CLASS="LITERAL"
>myfunc2(text, integer)</TT
>, <TT
CLASS="VARNAME"
>args[0]</TT
>
would contain the <TT
CLASS="TYPE"
>text</TT
> argument and
<TT
CLASS="VARNAME"
>args[1]</TT
> the <TT
CLASS="TYPE"
>integer</TT
> argument.
</P
><P
> The global dictionary <TT
CLASS="VARNAME"
>SD</TT
> is available to store
data between function calls. This variable is private static data.
The global dictionary <TT
CLASS="VARNAME"
>GD</TT
> is public data,
available to all Python functions within a session. Use with
care.<A
NAME="AEN36802"
></A
>
</P
><P
> Each function gets its own execution environment in the
Python interpreter, so that global data and function arguments from
<CODE
CLASS="FUNCTION"
>myfunc</CODE
> are not available to
<CODE
CLASS="FUNCTION"
>myfunc2</CODE
>. The exception is the data in the
<TT
CLASS="VARNAME"
>GD</TT
> dictionary, as mentioned above.
</P
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