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#------------------------------------------------------------------------------
# Copyright (c) 2016, 2021, Oracle and/or its affiliates. All rights reserved.
#------------------------------------------------------------------------------
#------------------------------------------------------------------------------
# subclassing.py
#
# Demonstrate how to subclass connections and cursors in order to add
# additional functionality (like logging) or create specialized interfaces for
# paticular applications.
#------------------------------------------------------------------------------
import cx_Oracle as oracledb
import sample_env
# sample subclassed connection which overrides the constructor (so no
# parameters are required) and the cursor() method (so that the subclassed
# cursor is returned instead of the default cursor implementation)
class Connection(oracledb.Connection):
def __init__(self):
connect_string = sample_env.get_main_connect_string()
print("CONNECT to database")
super().__init__(connect_string)
def cursor(self):
return Cursor(self)
# sample subclassed cursor which overrides the execute() and fetchone()
# methods in order to perform some simple logging
class Cursor(oracledb.Cursor):
def execute(self, statement, args):
print("EXECUTE", statement)
print("ARGS:")
for arg_index, arg in enumerate(args):
print(" ", arg_index + 1, "=>", repr(arg))
return super().execute(statement, args)
def fetchone(self):
print("FETCH ONE")
return super().fetchone()
# create instances of the subclassed connection and cursor
connection = Connection()
cursor = connection.cursor()
# demonstrate that the subclassed connection and cursor are being used
cursor.execute("select count(*) from ChildTable where ParentId = :1", (30,))
count, = cursor.fetchone()
print("COUNT:", int(count))
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