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https://github.com/psycopg/psycopg2.git
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91 lines
2.9 KiB
Python
91 lines
2.9 KiB
Python
# binary.py - working with binary data
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#
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# Copyright (C) 2001-2010 Federico Di Gregorio <fog@debian.org>
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#
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# psycopg2 is free software: you can redistribute it and/or modify it
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# under the terms of the GNU Lesser General Public License as published
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# by the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# psycopg2 is distributed in the hope that it will be useful, but WITHOUT
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# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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# FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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# License for more details.
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## put in DSN your DSN string
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DSN = 'dbname=test'
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## don't modify anything below this line (except for experimenting)
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from __future__ import print_function
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import sys
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import psycopg2
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if len(sys.argv) > 1:
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DSN = sys.argv[1]
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print("Opening connection using dsn:", DSN)
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conn = psycopg2.connect(DSN)
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print("Encoding for this connection is", conn.encoding)
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curs = conn.cursor()
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try:
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curs.execute("CREATE TABLE test_binary (id int4, name text, img bytea)")
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except:
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conn.rollback()
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curs.execute("DROP TABLE test_binary")
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curs.execute("CREATE TABLE test_binary (id int4, name text, img bytea)")
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conn.commit()
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# first we try two inserts, one with an explicit Binary call and the other
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# using a buffer on a file object.
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data1 = {'id':1, 'name':'somehackers.jpg',
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'img':psycopg2.Binary(open('somehackers.jpg').read())}
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data2 = {'id':2, 'name':'whereareyou.jpg',
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'img':buffer(open('whereareyou.jpg').read())}
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curs.execute("""INSERT INTO test_binary
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VALUES (%(id)s, %(name)s, %(img)s)""", data1)
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curs.execute("""INSERT INTO test_binary
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VALUES (%(id)s, %(name)s, %(img)s)""", data2)
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# now we try to extract the images as simple text strings
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print("Extracting the images as strings...")
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curs.execute("SELECT * FROM test_binary")
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for row in curs.fetchall():
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name, ext = row[1].split('.')
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new_name = name + '_S.' + ext
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print(" writing %s to %s ..." % (name+'.'+ext, new_name), end=' ')
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open(new_name, 'wb').write(row[2])
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print("done")
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print(" python type of image data is", type(row[2]))
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# extract exactly the same data but using a binary cursor
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print("Extracting the images using a binary cursor:")
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curs.execute("""DECLARE zot CURSOR FOR
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SELECT img, name FROM test_binary FOR READ ONLY""")
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curs.execute("""FETCH ALL FROM zot""")
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for row in curs.fetchall():
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name, ext = row[1].split('.')
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new_name = name + '_B.' + ext
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print(" writing %s to %s ..." % (name+'.'+ext, new_name), end=' ')
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open(new_name, 'wb').write(row[0])
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print("done")
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print(" python type of image data is", type(row[0]))
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# this rollback is required because we can't drop a table with a binary cursor
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# declared and still open
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conn.rollback()
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curs.execute("DROP TABLE test_binary")
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conn.commit()
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print("\nNow try to load the new images, to check it worked!")
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