Chapter 9. PyGreSQL - Python Interface
- Table of Contents
- 9.1. The pg Module
- 9.2. pg Module Functions
- connect -- opens a connection to the database server
- get_defhost -- get default host name [DV]
- set_defhost -- set default host name [DV]
- get_defport -- get default port [DV]
- set_defport -- set default port [DV]
- get_defopt -- get default options specification [DV]
- set_defopt -- set options specification [DV]
- get_deftty -- get default connection debug terminal specification [DV]
- set_deftty -- set default debug terminal specification [DV]
- get_defbase -- get default database name specification [DV]
- set_defbase -- set default database name specification [DV]
- 9.3. Connection object:
pgobject - query -- executes a SQL command
- reset -- resets the connection
- close -- close the database connection
- fileno -- returns the socket used to connect to the database
- getnotify -- gets the last notify from the server
- inserttable -- inserts a list into a table
- putline -- writes a line to the server socket [DA]
- getline -- gets a line from server socket [DA]
- endcopy -- synchronizes client and server [DA]
- locreate -- creates of large object in the database [LO]
- getlo -- builds a large object from given oid [LO]
- loimport -- imports a file to a PostgreSQL large object [LO]
- 9.4. Database wrapper class:
DB - pkey -- returns the primary key of a table
- get_databases -- get list of databases in the system
- get_tables -- get list of tables in connected database
- get_attnames -- returns the attribute names of a table
- get -- get a tuple from a database table
- insert -- insert a tuple into a database table
- update -- update a database table
- clear -- clear a database table
- delete -- deletes the row from a table
- 9.5. Query result object: pgqueryobject
- getresult -- gets the values returned by the query
- dictresult -- like getresult but returns a list of dictionaries
- listfields -- lists the fields names of the query result
- fieldname -- field number-name conversion
- fieldnum -- field name-number conversion
- ntuples -- returns the number of tuples in query object
- 9.6. Large Object:
pglarge - open -- opens a large object
- close -- closes the large object
- read -- reads from the large object
- write -- writes to the large object
- seek -- change current position in the large object
- tell -- returns current position in the large object
- unlink -- deletes the large object
- size -- gives the large object size
- export -- saves the large object to file
- 9.7. DB-API Interface
Author: Written by D'Arcy J.M. Cain (
<darcy@druid.net>). Based heavily on code written by Pascal Andre<andre@chimay.via.ecp.fr>. Copyright © 1995, Pascal Andre. Further modifications Copyright © 1997-2000 by D'Arcy J.M. Cain.
9.1. The pg Module
You may either choose to use the old mature interface provided by the pg module or otherwise the newer pgdb interface compliant with the DB-API 2.0 specification developed by the Python DB-SIG.
Here we describe only the older pg API. As long as PyGreSQL does not contain a description of the DB-API you should read about the API at http://www.python.org/topics/database/DatabaseAPI-2.0.html.
A tutorial-like introduction to the DB-API can be found at http://www2.linuxjournal.com/lj-issues/issue49/2605.html
The pg module defines three objects:
pgobject, which handles the connection and all the requests to the database,pglargeobject, which handles all the accesses to PostgreSQL large objects, andpgqueryobject that handles query results.
If you want to see a simple example of the use of some of these functions, see http://www.druid.net/rides where I have a link at the bottom to the actual Python code for the page.
9.1.1. Constants
Some constants are defined in the pg module dictionary. They are intended to be used as a parameters for methods calls. You should refer to the libpq description (Chapter 1) for more information about them. These constants are:
INV_READINV_WRITElarge objects access modes, used by
(pgobject.)locreateand(pglarge.)open.SEEK_SETSEEK_CURSEEK_ENDpositional flags, used by
(pglarge.)seek.version__version__constants that give the current version
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