Module functions and constants

The pgdb module defines a connect() function that allows to connect to a database, some global constants describing the capabilities of the module as well as several exception classes.

connect – Open a PostgreSQL connection

pgdb.connect([dsn][, user][, password][, host][, database])

Return a new connection to the database

Parameters:
  • dsn (str) – data source name as string
  • user (str) – the database user name
  • password (str) – the database password
  • host (str) – the hostname of the database
  • database – the name of the database
Returns:

a connection object

Return type:

pgdbCnx

Raises:

pgdb.OperationalError – error connecting to the database

This function takes parameters specifying how to connect to a PostgreSQL database and returns a pgdbCnx object using these parameters. If specified, the dsn parameter must be a string with the format 'host:base:user:passwd:opt:tty'. All of the parts specified in the dsn are optional. You can also specify the parameters individually using keyword arguments, which always take precedence. The host can also contain a port if specified in the format 'host:port'. In the opt part of the dsn you can pass command-line options to the server, the tty part is used to send server debug output.

Example:

con = connect(dsn='myhost:mydb', user='guido', password='234$')

Module constants

pgdb.apilevel

The string constant '2.0', stating that the module is DB-API 2.0 level compliant.

pgdb.threadsafety

The integer constant 1, stating that the module itself is thread-safe, but the connections are not thread-safe, and therefore must be protected with a lock if you want to use them from different threads.

pgdb.paramstyle

The string constant pyformat, stating that parameters should be passed using Python extended format codes, e.g. " ... WHERE name=%(name)s".

Errors raised by this module

The errors that can be raised by the pgdb module are the following:

exception pgdb.Warning

Exception raised for important warnings like data truncations while inserting.

exception pgdb.Error

Exception that is the base class of all other error exceptions. You can use this to catch all errors with one single except statement. Warnings are not considered errors and thus do not use this class as base.

exception pgdb.InterfaceError

Exception raised for errors that are related to the database interface rather than the database itself.

exception pgdb.DatabaseError

Exception raised for errors that are related to the database.

In PyGreSQL, this also has a DatabaseError.sqlstate attribute that contains the SQLSTATE error code of this error.

exception pgdb.DataError

Exception raised for errors that are due to problems with the processed data like division by zero or numeric value out of range.

exception pgdb.OperationalError

Exception raised for errors that are related to the database’s operation and not necessarily under the control of the programmer, e.g. an unexpected disconnect occurs, the data source name is not found, a transaction could not be processed, or a memory allocation error occurred during processing.

exception pgdb.IntegrityError

Exception raised when the relational integrity of the database is affected, e.g. a foreign key check fails.

exception pgdb.ProgrammingError

Exception raised for programming errors, e.g. table not found or already exists, syntax error in the SQL statement or wrong number of parameters specified.

exception pgdb.NotSupportedError

Exception raised in case a method or database API was used which is not supported by the database.