mirror of
https://github.com/psycopg/psycopg2.git
synced 2024-09-21 11:18:49 +03:00
64 lines
1.8 KiB
Python
64 lines
1.8 KiB
Python
# cursor.py - how to subclass the cursor type
|
|
#
|
|
# Copyright (C) 2004 Federico Di Gregorio <fog@debian.org>
|
|
#
|
|
# This program is free software; you can redistribute it and/or modify
|
|
# it under the terms of the GNU General Public License as published by the
|
|
# Free Software Foundation; either version 2, or (at your option) any later
|
|
# version.
|
|
#
|
|
# This program is distributed in the hope that it will be useful, but
|
|
# WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY
|
|
# or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
|
|
# for more details.
|
|
|
|
## put in DSN your DSN string
|
|
|
|
DSN = 'dbname=test'
|
|
|
|
## don't modify anything below this line (except for experimenting)
|
|
|
|
import sys
|
|
import psycopg2
|
|
import psycopg2.extensions
|
|
|
|
if len(sys.argv) > 1:
|
|
DSN = sys.argv[1]
|
|
|
|
print "Opening connection using dsn:", DSN
|
|
conn = psycopg2.connect(DSN)
|
|
print "Encoding for this connection is", conn.encoding
|
|
|
|
|
|
class NoDataError(psycopg2.ProgrammingError):
|
|
"""Exception that will be raised by our cursor."""
|
|
pass
|
|
|
|
class Cursor(psycopg2.extensions.cursor):
|
|
"""A custom cursor."""
|
|
|
|
def fetchone(self):
|
|
"""Like fetchone but raise an exception if no data is available.
|
|
|
|
Note that to have .fetchmany() and .fetchall() to raise the same
|
|
exception we'll have to override them too; even if internally psycopg
|
|
uses the same function to fetch rows, the code path from Python is
|
|
different.
|
|
"""
|
|
d = psycopg2.extensions.cursor.fetchone(self)
|
|
if d is None:
|
|
raise NoDataError("no more data")
|
|
return d
|
|
|
|
curs = conn.cursor(cursor_factory=Cursor)
|
|
curs.execute("SELECT 1 AS foo")
|
|
print "Result of fetchone():", curs.fetchone()
|
|
|
|
# now let's raise the exception
|
|
try:
|
|
curs.fetchone()
|
|
except NoDataError, err:
|
|
print "Exception caugth:", err
|
|
|
|
conn.rollback()
|