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# binary.py - working with binary data
#
# Copyright (C) 2001-2004 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 tis line (except for experimenting)
import sys
import psycopg2
if len(sys.argv) > 1:
DSN = sys.argv[1]
print "Opening connection using dns:", DSN
conn = psycopg2.connect(DSN)
print "Encoding for this connection is", conn.encoding
curs = conn.cursor()
try:
curs.execute("CREATE TABLE test_binary (id int4, name text, img bytea)")
except:
conn.rollback()
curs.execute("DROP TABLE test_binary")
curs.execute("CREATE TABLE test_binary (id int4, name text, img bytea)")
conn.commit()
# first we try two inserts, one with an explicit Binary call and the other
# using a buffer on a file object.
data1 = {'id':1, 'name':'somehackers.jpg',
'img':psycopg2.Binary(open('somehackers.jpg').read())}
data2 = {'id':2, 'name':'whereareyou.jpg',
'img':buffer(open('whereareyou.jpg').read())}
curs.execute("""INSERT INTO test_binary
VALUES (%(id)s, %(name)s, %(img)s)""", data1)
curs.execute("""INSERT INTO test_binary
VALUES (%(id)s, %(name)s, %(img)s)""", data2)
# now we try to extract the images as simple text strings
print "Extracting the images as strings..."
curs.execute("SELECT * FROM test_binary")
for row in curs.fetchall():
name, ext = row[1].split('.')
new_name = name + '_S.' + ext
print " writing %s to %s ..." % (name+'.'+ext, new_name),
open(new_name, 'wb').write(row[2])
print "done"
print " python type of image data is", type(row[2])
# extract exactly the same data but using a binary cursor
print "Extracting the images using a binary cursor:"
curs.execute("""DECLARE zot CURSOR FOR
SELECT img, name FROM test_binary FOR READ ONLY""")
curs.execute("""FETCH ALL FROM zot""")
for row in curs.fetchall():
name, ext = row[1].split('.')
new_name = name + '_B.' + ext
print " writing %s to %s ..." % (name+'.'+ext, new_name),
open(new_name, 'wb').write(row[0])
print "done"
print " python type of image data is", type(row[0])
# this rollback is requires because we can't drop a table with a binary cusor
# declared and still open
conn.rollback()
curs.execute("DROP TABLE test_binary")
conn.commit()
print "\nNow try to load the new images, to check it worked!"
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