The document shows how to connect to a PostgreSQL database called pgsqldemodb using Python. It creates a table called pgsqldemotable with two columns, inserts some rows, runs a select query to retrieve the data, inserts additional rows using Python scripts, and confirms the new rows were added by running another select query in psql.

1. selvamani@selvamani-laptop:~$ sudo su - postgres
[sudo] password for selvamani:
postgres@selvamani-laptop:~$ psql -U pgsqldemouser pgsqldemodb
psql (8.4.3)
Type "help" for help.
pgsqldemodb=> create table pgsqldemotable(sno varchar(3), name varchar(30));
CREATE TABLE
pgsqldemodb=> insert into pgsqldemotable values('1','Arulalan');
INSERT 0 1
pgsqldemodb=> insert into pgsqldemotable values('2','BalaKrishnan');
INSERT 0 1
pgsqldemodb=> insert into pgsqldemotable values('3','Dhasthagheer');
INSERT 0 1
pgsqldemodb=> insert into pgsqldemotable values('4','Selvamani');
INSERT 0 1
pgsqldemodb=> select * from pgsqldemotable;
sno | name
-----+--------------
1 | Arulalan
2 | BalaKrishnan
3 | Dhasthagheer
4 | Selvamani
(4 rows)
pgsqldemodb=> alter role pgsqldemouser with password 'demo';
ALTER ROLE
pgsqldemodb=> q
postgres@selvamani-laptop:~$ logout
selvamani@selvamani-laptop:~$ python
Python 2.6.4 (r264:75706, Dec 7 2009, 18:45:15)
[GCC 4.4.1] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import psycopg2
>>> connection=psycopg2.connect("host=localhost dbname=pgsqldemodb user=pgsqldemouser
password=demo")
cur=connection.cursor()
>>> cur.execute("""select * from pgsqldemotable""")
>>> a=cur.fetchall()
>>> print a
[('1', 'Arulalan'), ('2', 'BalaKrishnan'),('3','Dhasthagheer'), ('4', 'Selvamani')]
>>> type(a)
<type 'list'>
>>> type(a[0])
<type 'tuple'>
>>> type(a[0][0])
<type 'str'>
>>> type(a[0][1])
<type 'str'>
>>> a[0][1]
'Arulalan'
>>> a[1][1]

2. 'BalaKrishnan'
>>> cur.execute("""insert into pgsqldemotable values('5','Rajkumar')""")
>>> connection.commit()
>>> sno=raw_input("""Enter the value:""")
Enter the value:6
>>> name=raw_input("""Enter the value:""")
Enter the value:Shrinivasan
>>> cur.execute("""insert into pgsqldemotable values('%s','%s')""" %(sno,name))
>>> connection.commit()
>>> exit()
selvamani@selvamani-laptop:~$ sudo su - postgres
postgres@selvamani-laptop:~$ psql -U pgsqldemouser -W pgsqldemodb
Password for user pgsqldemouser:
psql (8.4.3)
Type "help" for help.
pgsqldemodb=> select * from pgsqldemotable;
sno | name
-----+--------------
1 | Arulalan
2 | BalaKrishnan
3 | Dhasthagheer
4 | Selvamani
5 | Rajkumar
6 | Shrinivasan
(6 rows)
pgsqldemodb=> q
postgres@selvamani-laptop:~$ logout
selvamani@selvamani-laptop:~$