psycopg2/examples/copy_from.py

# copy_from.py -- example about copy_from 
#
# Copyright (C) 2002 Tom Jenkins <tjenkins@devis.com>
# Copyright (C) 2005 Federico Di Gregorio <fog@initd.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)

import sys
import os
import StringIO
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_copy (fld1 text, fld2 text, fld3 int4)")
except:
    conn.rollback()
    curs.execute("DROP TABLE test_copy")
    curs.execute("CREATE TABLE test_copy (fld1 text, fld2 text, fld3 int4)")
conn.commit()

# copy_from with default arguments, from open file

io = open('copy_from.txt', 'wr')
data = ['Tom\tJenkins\t37\n',
        'Madonna\t\\N\t45\n',
        'Federico\tDi Gregorio\t\\N\n']
io.writelines(data)
io.close()

io = open('copy_from.txt', 'r')
curs.copy_from(io, 'test_copy')
print("1) Copy %d records from file object " % len(data) +
      "using defaults (sep: \\t and null = \\N)")
io.close()

curs.execute("SELECT * FROM test_copy")
rows = curs.fetchall()
print("   Select returned %d rows" % len(rows))

for r in rows:
    print("    %s %s\t%s" % (r[0], r[1], r[2]))
curs.execute("delete from test_copy")
conn.commit()

# copy_from using custom separator, from open file

io = open('copy_from.txt', 'wr')
data = ['Tom:Jenkins:37\n',
        'Madonna:\N:45\n',
        'Federico:Di Gregorio:\N\n']
io.writelines(data)
io.close()

io = open('copy_from.txt', 'r')
curs.copy_from(io, 'test_copy', ':')
print("2) Copy %d records from file object using sep = :" % len(data))
io.close()

curs.execute("SELECT * FROM test_copy")
rows = curs.fetchall()
print("   Select returned %d rows" % len(rows))

for r in rows:
    print("    %s %s\t%s" % (r[0], r[1], r[2]))
curs.execute("delete from test_copy")
conn.commit()

# copy_from using custom null identifier, from open file

io = open('copy_from.txt', 'wr')
data = ['Tom\tJenkins\t37\n',
        'Madonna\tNULL\t45\n',
        'Federico\tDi Gregorio\tNULL\n']
io.writelines(data)
io.close()

io = open('copy_from.txt', 'r')
curs.copy_from(io, 'test_copy', null='NULL')
print("3) Copy %d records from file object using null = NULL" % len(data))
io.close()

curs.execute("SELECT * FROM test_copy")
rows = curs.fetchall()
print("   Select using cursor returned %d rows" % len(rows))

for r in rows:
    print("    %s %s\t%s" % (r[0], r[1], r[2]))
curs.execute("delete from test_copy")
conn.commit()

# copy_from using custom separator and null identifier

io = open('copy_from.txt', 'wr')
data = ['Tom:Jenkins:37\n', 'Madonna:NULL:45\n', 'Federico:Di Gregorio:NULL\n']
io.writelines(data)
io.close()

io = open('copy_from.txt', 'r')
curs.copy_from(io, 'test_copy', ':', 'NULL')
print("4) Copy %d records from file object " % len(data) +
      "using sep = : and null = NULL")
io.close()

curs.execute("SELECT * FROM test_copy")
rows = curs.fetchall()
print("   Select using cursor returned %d rows" % len(rows))

for r in rows:
    print("    %s %s\t%s" % (r[0], r[1], r[2]))
curs.execute("delete from test_copy")
conn.commit()

# anything can be used as a file if it has .read() and .readline() methods

data = StringIO.StringIO()
data.write('\n'.join(['Tom\tJenkins\t37',
                      'Madonna\t\N\t45',
                      'Federico\tDi Gregorio\t\N']))
data.seek(0)

curs.copy_from(data, 'test_copy')
print("5) Copy 3 records from StringIO object using defaults")

curs.execute("SELECT * FROM test_copy")
rows = curs.fetchall()
print("   Select using cursor returned %d rows" % len(rows))

for r in rows:
    print("    %s %s\t%s" % (r[0], r[1], r[2]))
curs.execute("delete from test_copy")
conn.commit()

# simple error test

print("6) About to raise an error")
data = StringIO.StringIO()
data.write('\n'.join(['Tom\tJenkins\t37',
                      'Madonna\t\N\t45',
                      'Federico\tDi Gregorio\taaa']))
data.seek(0)

try:
    curs.copy_from(data, 'test_copy')
except StandardError as err:
    conn.rollback()
    print("   Caught error (as expected):\n", err)

conn.rollback()

curs.execute("DROP TABLE test_copy")
os.unlink('copy_from.txt')
conn.commit()