Disclaimer

The following is a HOWTO document for installing Python with iODBC on Linux or Unix. Feel free to criticize, suggest modifications, or ask further questions. It is currently maintained by Tim Haynes of Openlink Software (iodbc@openlinksw.com)

Prerequisites include basic Unix familiarity, such as creating directories and users, using an editor, etc.

This HOWTO is intended to assist in connecting python to back-end databases via ODBC in a development environment and should not take the place of thorough testing before deployment on a production system.

ODBC Overview

ODBC (Open Database Connectivity) is an operating system- and database- independent communication API for database connectivity. It enables ODBC compliant client applications to connect transparently to back-end databases via ODBC function calls which are implemented by ODBC Drivers for target back-end databases.

ODBC provides your applications with database-independence; consequentially, you no longer have to incur the development and maintenance cost of inextricably binding your application to backend database engines via their proprietary data-access (aka native) APIs.

ODBC connections involve an ODBC-compliant Application or Data Access Layer, ODBC Driver Manager, ODBC Driver, and back-end Database. The ODBC Driver Manager for Microsoft Windows platforms is administered via the ODBC Administrator Control Panel applet at setup and configuration time. The Driver Manager registers a set of ODBC driver connection parameters called a Data Source Name (DSN), and maintains (in persistent form) a relationship between the DSN and an underlying ODBC Driver that will honor data access request via that DSN.

At runtime an application looks to the driver manager for a DSN, and then passes the connection parameters specified in the DSN to the appropriate driver, which makes the actual database connection. Under non-Windows platforms you may need to install a Driver Manager if this isn't delivered as an integral part of your operating environment. Platform independent ODBC (aka iODBC) is an Open Source ODBC project (dual license LGPL / BSD)for non Windows platforms maintained by OpenLink Software that consists of an ODBC SDK (libraries and header files) and ODBC Runtime components (Administrator and Driver Manager).

Preface

You will also need an ODBC Driver and Database to complete the architecture.

If you need ODBC drivers to connect to a third-party database on the same or another machine, OpenLink ODBC Drivers are available, and may be downloaded from http://www.openlinksw.com

The Virtuoso database may also be downloaded from http://virtuoso.openlinksw.com/

Both sets of ODBC Drivers are available on a free 30 day evaluation basis.

Support for setting up the OpenLink Drivers may be obtained at http://support.openlinksw.com/

Installing Python

If you already have Python installed and running, you probably do not need to rebuild it. Otherwise, you can compile it from source if you wish, thus:

First, download the latest source distribution from http://www.python.org/ - currently this is version 2.2.3.

Unpack it into a build directory with the command

gzip -cd < Python-2.2.3.tgz | tar xvpf -

Enter the build directory, and run configure, specifying any optional configurations as desired:

cd Python-2.2.3/
zsh, purple  2:50PM Python-2.2.3/ % ./configure --help
Usage: configure [options] [host]
Options: [defaults in brackets after descriptions]
Configuration:
--cache-file=FILE       cache test results in FILE
[snip]
Directory and file names:
--prefix=PREFIX         install architecture-independent files in PREFIX
[/usr/local]
[snip]
--with-libs='lib1 ...'          link against additional libs
--with-signal-module            disable/enable signal module
--with-dec-threads              use DEC Alpha/OSF1 thread-safe libraries
--with(out)-threads[=DIRECTORY] disable/enable thread support
[snip]
zsh, purple  2:50PM Python-2.2.3/ % ./configure --prefix=/usr/local/stow/python-2.2.3
creating cache ./config.cache
checking MACHDEP... linux2
checking for --without-gcc... no
checking for --with-cxx=<compiler>... no
checking for c++... g++
checking whether the C++ compiler (g++  ) works... yes
checking whether the C++ compiler (g++  ) is a cross-compiler... no
[snip]
creating Makefile.pre
creating Modules/Setup.config
creating pyconfig.h
creating Setup
creating Setup.local
creating Makefile
zsh, purple  2:52PM Python-2.2.3/ % make
gcc -c -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -I. -I./Include -DHAVE_CONFIG_H  -o Modules/python.o Modules/python.c
gcc -c -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -I. -I./Include -DHAVE_CONFIG_H  -o Parser/acceler.o Parser/acceler.c
running build_scripts
creating build/scripts-2.2
copying and adjusting /home/tim/public_html/docs/python-HOWTO/Python-2.2.3/Tools/scripts/pydoc -> build/scripts-2.2
zsh, purple  2:59PM Python-2.2.3/ % su
bash-2.05b# make install
[snip]
Creating directory /usr/local/stow/python-2.2.3/man
Creating directory /usr/local/stow/python-2.2.3/man/man1
/bin/install -c -m 644 ./Misc/python.man        /usr/local/stow/python-2.2.3/man/man1/python.1

Installing iODBC

If you do not already have iODBC installed, either install an RPM from iODBC.org, or install from source:

Compiling iODBC from source

Requirements: C-compiler; optionally gtk+-1.2 (required if building from CVS).

As before, unpack the iODBC sources, enter the build directory, configure, make and make install:

zsh, purple  4:13PM C/ % tar xvpfz libiodbc-3.51.1.tar.gz
libiodbc-3.51.1/
libiodbc-3.51.1/admin/
libiodbc-3.51.1/admin/Makefile.am
libiodbc-3.51.1/admin/Makefile.in
libiodbc-3.51.1/admin/acinclude.m4
[snip]
libiodbc-3.51.1/samples/Makefile.in
libiodbc-3.51.1/samples/iodbctest.c
zsh, purple  4:14PM C/ % cd libiodbc-3.51.1
zsh, purple  4:14PM libiodbc-3.51.1/ % ./configure --prefix=/usr/local/stow/iodbc-3.51.1
checking for a BSD-compatible install... /bin/install -c
checking whether build environment is sane... yes
checking for gawk... gawk
[snip]
config.status: executing depfiles commands
config.status: executing default commands
zsh, purple  4:15PM libiodbc-3.51.1/ % make
Making all in admin
make[1]: Entering directory `/home/tim/C/libiodbc-3.51.1/admin'
[snip]
make[1]: Leaving directory `/home/tim/C/libiodbc-3.51.1'
zsh, purple  4:15PM libiodbc-3.51.1/ % su root -c 'make install'

It's advisable to install into /usr/local, or stow your installation into /usr/local, as that is searched by most other applications trying to locate iODBC.

Testing ODBC

Now is a good time to configure iODBC, by adding a DSN - create a file ~/.odbc.ini, edit it to look something like this:

[ODBC Data Sources]
PostgreSQL native localhost = PostgreSQL native driver
Local Virtuoso Demo = localhost virtuoso (demo instance)
Local Virtuoso = localhost virtuoso

[Local Virtuoso Demo]
Description = Virtuoso 3.1
Driver      = /home/tim/virtuoso/lib/virtodbc31.so
Address     = localhost:1112
UserName    = dba
User        = dba

[Local Virtuoso]
Description = Virtuoso 3.1
Driver      = /home/tim/virtuoso/lib/virtodbc31.so
Address     = localhost:1111
UserName    = dba
User        = dba

[PostgreSQL native localhost]
Driver     = /usr/lib/postgresql/lib/libodbcpsql.so
Host       = localhost
Server     = localhost
ServerName = localhost
Database   = tim
UserName   = tim
UID        = tim
Port       = 5432

It is advisable to export the environment variable ODBCINI to point to this file, too - depending on your shell, either:

echo 'export ODBCINI=$HOME/.odbc.ini' >> .bashrc

or

echo 'setenv ODBCINI $HOME/.odbc.ini' >> .tcshrc

as appropriate.

You can now make a test connection with the iodbctest utility, thus:

zsh, purple  4:54PM libiodbc-3.51.1/ % which iodbctest
/usr/local/bin//iodbctest
zsh, purple  4:54PM libiodbc-3.51.1/ % iodbctest      
iODBC Demonstration program
This program shows an interactive SQL processor
Driver Manager: 03.51.0001.0908

Enter ODBC connect string (? shows list): ?

DSN                            | Description                   
---------------------------------------------------------------
Local Virtuoso                 | localhost virtuoso 
Local Virtuoso Demo            | localhost virtuoso (demo instance)
MySQL                          | MySQL native driver           
PostgreSQL native localhost    | PostgreSQL native driver      
PostgreSQL OpenLink localhost  | PostgreSQL over OpenLink multi-tier
Virtuoso30                     | OpenLink Virtuoso 3.0         

Enter ODBC connect string (? shows list): DSN=Local Virtuoso Demo;UID=dba;PWD=cens0red
Driver: 03.50.2505 OpenLink Virtuoso ODBC Driver

SQL>

If you see the SQL> prompt there, then all has gone well.

Building Egenix' mxODBC module

The last infrastructure hurdle to overcome is the building of Egenix's mxODBC module; download the sources from http://www.egenix.com/files/python/mxODBC.html, and run the following:

zsh, purple  4:21PM egenix-mx-commercial-2.0.6/ % python setup.py install

This requires root privileges, and will install in your python site-packages directory, thus:

zsh, purple  4:24PM tim/ % ls /usr/lib/python2.2/site-packages/mx/ODBC 
COPYRIGHT  LazyModule.py   Misc/     ODBC.pyo     __init__.pyc  unixODBC/
Doc/       LazyModule.pyc  ODBC.py   README       __init__.pyo
LICENSE    LazyModule.pyo  ODBC.pyc  __init__.py  iODBC/

Sample script to use the module

Finally, a small script to link it all together. You can use this to test simple functionality of iODBC, mxODBC and Python.

#!/usr/bin/python

import mx.ODBC.iODBC

dsn="Local Virtuoso Demo"

conn=mx.ODBC.iODBC.Connect (dsn, "dba", "cens0red")

print "Content-Type: text/plain

"
print "Database Type: " + conn.getinfo (17)[1] + "
"

curshandle=conn.cursor()

print "Top 10 in Shippers table:"
curshandle.execute ("select top 10 * from Demo.demo.Shippers")
for i in curshandle.fetchall():
print i

#print curshandle.fetchall()

print "
Creating and populating timtest table:"

try:
curshandle.execute ("drop table timtest") 
except: 
pass

curshandle.execute ("create table timtest (id integer, str varchar (255))")
curshandle.execute ("insert into timtest values (99, 'testing')")
curshandle.execute ("select * from timtest")

for i in curshandle.fetchall():
print i

On running it, you should see the following output:

zsh, purple 11:22AM python/ % ./dbi-test.py
Database Type: OpenLink Virtuoso

Top 10 in Shippers table:
(1, 'Speedy Express', '(503) 555-9831')
(2, 'United Package', '(503) 555-3199')
(3, 'Federal Shipping', '(503) 555-9931')

Creating and populating timtest table:
(99, 'testing')

References