import cx_Oracle
import decimal

conn = cx_Oracle.connect(
    user="scott",
    password="tiger",
    dsn=cx_Oracle.makedsn(
        "192.168.1.185", 1521, sid="xe",
    )
)

cursor = conn.cursor()


def output_type_handler(cursor, name, defaultType,
                        size, precision, scale):
    if defaultType == cx_Oracle.NUMBER:
        return cursor.var(
            cx_Oracle.STRING,
            255,
            outconverter=decimal.Decimal,
            arraysize=cursor.arraysize)

cursor.outputtypehandler = output_type_handler

cursor.execute("""
CREATE TABLE t (
    x NUMERIC(38, 12)
)
""")
try:
    value = decimal.Decimal("319438950232418390.273596")
    cursor.setinputsizes(x=cx_Oracle.NUMBER)
    cursor.execute(
        "INSERT INTO t (x) VALUES (:x)",
        x=value
    )

    cursor.execute("SELECT x FROM t")
    row = cursor.fetchone()
    received = row[0]

    print "cx_Oracle version: %r" % cx_Oracle.__version__
    print "Sent: %r   Received: %r" % (value, received)

    assert received == value, "%r != %r" % (received, value)


finally:
    cursor.execute("DROP TABLE t")

cx_Oracle version: '5.2'
Sent: Decimal('319438950232418390.273596')   Received: Decimal('319438950232418390.273596')

cx_Oracle version: '6.0'
Sent: Decimal('319438950232418390.273596')   Received: Decimal('319438950232418000')
Traceback (most recent call last):
  File "test.py", line 46, in <module>
    assert received == value, "%r != %r" % (received, value)
AssertionError: Decimal('319438950232418000') != Decimal('319438950232418390.273596')