The PL/Python procedural language allows PostgreSQL functions to be written in the Python language.
To install PL/Python in a particular database, use createlang plpython dbname.
Note: 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.
The Python code you write gets transformed into a function. E.g.,
CREATE FUNCTION myfunc(text) RETURNS text
AS 'return args[0]'
LANGUAGE 'plpython';
gets transformed into
def __plpython_procedure_myfunc_23456():
return args[0]
where 23456 is the OID of the function.
If you do not provide a return value, Python returns the default None which may or may not be what you want. The language module translates Python's None into the SQL null value.
The PostgreSQL function
parameters are available in the global args list. In the myfunc example, args[0] contains whatever was passed in as the
text argument. For myfunc2(text,
integer), args[0] would
contain the text variable and
args[1] the integer variable.
The global dictionary SD is
available to store data between function calls. This variable
is private static data. The global dictionary GD is public data, available to all Python
functions within a session. Use with care.
Each function gets its own restricted execution object in
the Python interpreter, so that global data and function
arguments from myfunc are not
available to myfunc2. The
exception is the data in the GD
dictionary, as mentioned above.