Python Driver

CUBRIDdb is a Python extension package that implements Python Database API 2.0 compliant support for CUBRID. In additional to the minimal feature set of the standard Python DB API, CUBRID Python API also exposes nearly the entire native client API of the database engine in _cubrid.

CUBRID Python driver is written based on CCI API so affected by CCI configurations such as CCI_DEFAULT_AUTOCOMMIT.

Installing and Configuring Python

Linux/UNIX

There are three ways to install CUBRID Python driver on Linux, UNIX, and UNIX-like operating systems. You can find instructions for each of them below.

Requirements

Installing CUBRID Python Driver using Yum (Fedora or CentOS)

  1. To install CUBRID Python driver by using the yum command, you need to tell Yum where to look for CUBRID package. First, visit one of the following links depending on your operating system.

    For the example to install CUBRID 9.0 on Fedora 17 is as follows: (fc17 means this operating system version).

    rpm -i http://yumrepository.cubrid.org/cubrid_repo_settings/9.0.0/cubridrepo-9.0.0-1.fc17.noarch.rpm
    
  2. Enter the command below to install CUBRID Python driver.

    yum install python-cubrid
    

Building CUBRID Python Driver from Source Code (Linux)

To install CUBRID Python driver by compiling source code, you should have Python Development Package installed on your system.

  1. Download the source code from http://www.cubrid.org/?mid=downloads&item=python_driver.

  2. Extract the archive to the desired location.

    tar xvfz cubrid-python-src-8.4.0.0001.tar.gz
    
  3. Navigate to the directory where you have extracted the source code.

    cd cubrid-python-src
    
  4. Build the driver. At this and next step, make sure you are still under the root user.

    python setup.py build
    
  5. Install the driver. Here you also need root privileges.

    python setup.py install
    

Using a Package Manager (EasyInstall) of CUBRID Python Driver (Linux)

EasyInstall is a Python module (easy_install) bundled with setuptools that lets you automatically download, build, install, and manage Python packages. It gives you a quick way to install packages remotely by connecting to other websites via HTTP as well as connecting to the Package Index. It is somewhat analogous to the CPAN and PEAR tools for Perl and PHP, respectively. For more information about EasyInstall, see http://packages.python.org/distribute/easy_install.html.

Enter the command below to install CUBRID Python driver by using EasyInstall.

easy_install CUBRID-Python

Windows

To install CUBRID Python driver on Windows, first download CUBRID Python driver as follows:

  • Visit the website below to download the driver. You will be given to select your operating system and Python version installed on your system.

    http://www.cubrid.org/?mid=downloads&item=python_driver&os=windows&python=detect

  • Extract the archive you downloaded. You should see a folder and two files in the folder. Copy these files to the Lib folder where your Python has been installed; by default, it is C:\Program Files\Python\Lib.

Python Programming

The CUBRIDdb package is supposed to have the following constants according to Python Database API 2.0.

Name Value
threadsafety 2
apilevel 2.0
paramstyle qmark

Python Sample Program

This sample program will show steps that you need to perform in order to connect to the CUBRID database and run SQL statements from Python programming language. Enter the command line below to create a new table in your database.

csql -u dba -c "CREATE TABLE posts( id integer, title varchar(255), body string, last_updated timestamp );" demodb

Connecting to demodb from Python

  1. Open a new Python console and enter the command line below to import CUBRID Python driver.

    import CUBRIDdb
    
  2. Establish a connection to the demodb database located on localhost.

    conn = CUBRIDdb.connect('CUBRID:localhost:30000:dba::')
    

For the demodb database, it is not required to enter any password. In a real-world scenario, you will have to provide the password to successfully connect. The syntax to use the connect () function is as follows:

connect (url[,user[password]])

If the database has not started and you try to connect to it, you will receive an error such as this:

Traceback (most recent call last):
  File "tutorial.py", line 3, in <module>
    conn = CUBRIDdb.connect('CUBRID:localhost:30000:dba::')
  File "/usr/local/lib/python2.6/site-packages/CUBRIDdb/__init__.py", line 48, in Connect
    return Connection(*args, **kwargs)
  File "/usr/local/lib/python2.6/site-packages/CUBRIDdb/connections.py", line 19, in __init__
    self._db = _cubrid.connect(*args, **kwargs)
_cubrid.Error: (-1, 'ERROR: DBMS, 0, Unknown DBMS Error')

If you provide wrong credentials, you will receive an error such as this:

Traceback (most recent call last):
  File "tutorial.py", line 3, in <module>
    con = CUBRIDdb.connect('CUBRID:localhost:33000:demodb','a','b')
  File "/usr/local/lib/python2.6/site-packages/CUBRIDdb/__init__.py", line 48, in Connect
    return Connection(*args, **kwargs)
  File "/usr/local/lib/python2.6/site-packages/CUBRIDdb/connections.py", line 19, in __init__
    self._db = _cubrid.connect(*args, **kwargs)
_cubrid.Error: (-1, 'ERROR: DBMS, 0, Unknown DBMS Error')

Executing an INSERT Statement

Now that the table is empty, insert data for the test. First, you have to obtain a cursor and then execute the INSERT statement.

cur = conn.cursor()
cur.execute("INSERT INTO posts (id, title, body, last_updated) VALUES (1, 'Title 1', 'Test body #1', CURRENT_TIMESTAMP)")
conn.commit()

The auto-commit in CUBRID Python driver is disabled by default. Therefore, you have to manually perform commit by using the commit () function after executing any SQL statement. This is equivalent to executing cur.execute(“COMMIT”) . The opposite to executing commit() is executing rollback (), which aborts the current transaction.

Another way to insert data is to use prepared statements. You can safely insert data into the database by defining a row that contains the parameters and passing it to the execute () function.

args = (2, 'Title 2', 'Test body #2')
cur.execute("INSERT INTO posts (id, title, body, last_updated) VALUES (?, ?, ?, CURRENT_TIMESTAMP)", args)

The entire script up to now looks like this:

import CUBRIDdb
conn = CUBRIDdb.connect('CUBRID:localhost:33000:demodb', 'public', '')
cur = conn.cursor()

# Plain insert statement
cur.execute("INSERT INTO posts (id, title, body, last_updated) VALUES (1, 'Title 1', 'Test body #1', CURRENT_TIMESTAMP)")

# Parameterized insert statement
args = (2, 'Title 2', 'Test body #2')
cur.execute("INSERT INTO posts (id, title, body, last_updated) VALUES (?, ?, ?, CURRENT_TIMESTAMP)", args)

conn.commit()

Fetching all records at a time

You can fetch entire records at a time by using the fetchall () function.

cur.execute("SELECT * FROM posts ORDER BY last_updated")
rows = cur.fetchall()
for row in rows:
    print row

This will return the two rows inserted earlier in the following form:

[1, 'Title 1', 'Test body #1', '2011-4-7 14:34:46']
[2, 'Title 2', 'Test body #2', '2010-4-7 14:34:46']

Fetching a single record at a time

In a scenario where a lot of data must be returned into the cursor, you can fetch only one row at a time by using the fetchone () function.

cur.execute("SELECT * FROM posts")
row = cur.fetchone()
while row:
    print row
    row = cur.fetchone()

Fetching as many as records desired at a time

You can fetch a specified number of records at a time by using the fetchmany () function.

cur.execute("SELECT * FROM posts")
rows = cur.fetchmany(3)
for row in rows:
    print row

Accessing Metadata on the Returned Data

If it is necessary to get information about column attributes of the obtained records, you should call the description method.

for description in cur.description:
    print description

The output of the script is as follows:

('id', 8, 0, 0, 0, 0, 0)
('title', 2, 0, 0, 255, 0, 0)
('body', 2, 0, 0, 1073741823, 0, 0)
('last_updated', 15, 0, 0, 0, 0, 0)

Each of row has the following information.

(column_name, data_type, display_size, internal_size, precision, scale, nullable)

For more information about numbers representing data types, see http://packages.python.org/CUBRID-Python/toc-CUBRIDdb.FIELD_TYPE-module.html .

Releasing Resource

After you have done using any cursor or connection to the database, you must release the resource by calling both object’s close () function.

cur.close()
conn.close()

Python API

Python Database API is composed of connect() module class, Connection object, Cursor object, and many other auxiliary functions. For more information, see Python DB API 2.0 Official Documentation at http://www.python.org/dev/peps/pep-0249/.

You can find the information about CUBRID Python API at http://ftp.cubrid.org/CUBRID_Docs/Drivers/Python/.