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# binary.py - working with binary data
#
# Copyright (C) 2001-2010 Federico Di Gregorio <fog@debian.org>
#
# psycopg2 is free software: you can redistribute it and/or modify it
# under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser 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)
from __future__ import print_function
import sys
import psycopg2
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)
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), end=' ')
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), end=' ')
open(new_name, 'wb').write(row[0])
print("done")
print(" python type of image data is", type(row[0]))
# this rollback is required because we can't drop a table with a binary cursor
# 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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