Merge from trunk

[plcapi.git] / trunk / psycopg2 / examples / binary.py

diff --git a/trunk/psycopg2/examples/binary.py b/trunk/psycopg2/examples/binary.py
new file mode 100644 (file)
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+++ b/trunk/psycopg2/examples/binary.py
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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!"