Calling Python from Oracle

Question

Is it possible to call Python within an Oracle procedure? I\'ve read plenty of literature about the reverse case (calling Oracle SQL from Python), but not the other way around.<

Answer 1

On the edge there is a possibility on how to overcome the PL/SQL limitations. You can design a specific interface between Database and Python program. I suppose You'd use one of the Python's library to get some data from the Net. And then exchange it's data with Oracle using the C Library.

call python using c library -> data file -> external table -> data

NOTICE: Take it as a proof of concept or rather starting point for deeper exploration. Also I'd strongly discourage You from using it on production. Breaking the PL/SQL jail to call system program could be considered at least as unsafe.

So this is the possible way on how to proceed:

--== Prerequisities ==--

pip install quandl

--== quandl.py ==--

#!/usr/bin/python
import quandl
# World Bank Education Statistics
# Population, tertiary, total - Czech Republic
data = quandl.get("WEDU/CZE_SP_TER_TOTL_IN")
data.to_csv("/u01/data/data.txt")

--== exec.c ==--

//
// gcc -Wall -fPIC -c exec.c
// gcc -shared -o exec.so exec.o
// mkdir -p /u01/lib
// cp exec.so /u01/lib
//

#include 

int execute() {
  system("/u01/bin/get_data.py");
  return 0; // We want to make the compiler happy
}

--== LISTENER CONFIGURATION ==--

SID_LIST_LISTENER =
...
  (SID_DESC =
...
    (ENVS="EXTPROC_DLLS=ANY")
    (PROGRAM = extproc)
...

--== DDL PART ==--

create or replace library c_exec is '/u01/lib/exec.so';

create or replace procedure exec as external
  name "execute"
  library c_exec
  language c;
/

create directory pydata as '/u01/data';

create table data (
  "date" varchar2(14),
  "value" varchar2(32)
) organization external (  
  type oracle_loader
  default directory pydata
  access parameters ( 
    records delimited by newline
    nobadfile nodiscardfile nologfile
    fields terminated by ','
   ) location (pydata:'data.txt')
  );

---=== USAGE ===---

--== DOWNLOAD DATA FOR PROCESSING ==--

Using the external PL/SQL C library You would call the python program that stores the result to the expected location for the external table.

execute exec;  

--== QUERY THE DATA ==--

select 
  to_date("date",'yyyy-mm-dd') "date", 
  to_number("value") "value" 
from data 
  where "date" != 'Date';

--== RESULT ==--

date           value
--------- ----------
31-DEC-70     886414
31-DEC-71     885549
31-DEC-72     877533
31-DEC-73     862859