Download cursor = db.cursor()

Python & Oracle
By Michael McLaughlin
Python cx_Oracle Tutorial
cx_Oracle Documentation
Objectives
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Introduce Python
Learn how to install cx_Oracle
Learn how to connect to Oracle
Learn how to run static SQL statements
Learn how to run dynamic SQL statements
Learn how to call PL/SQL store programs
Introduce Python
Python?
• A robust high-level programming language:
– Gets complex things done quickly
– Automate system and data integration tasks
– Solve complex analytical problems
Install cx_Oracle Driver
The cx_Oracle Driver
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Conforms to the Python DB API 2.0
Requires Oracle Client Installation
Not presently in standard Linux repos
You can download from here:
– https://pypi.python.org/pypi/cx_Oracle
Installing cx_Oracle Driver
• Things you need to know first:
– Ships for Linux/Unix in RPM file
– Ships for Windows in MS Windows Installer file
– Available for Python 2.6/2.7 on Linux/Unix
– Available for Python 2.6/2.7/3.4-3.6 on Windows
– Requires local Oracle Instant Client insall
• Supports platforms:
– Linux, Unix, Mac OS X, and Windows
Installation Steps (as root)
• Check your Python version with:
# python -V
• Check for Oracle Client installation:
# rpm –qa oracle-instantclient11-2-basic
• Check for Oracle Client installation:
# yum install -y /tmp/oracle-instantclient*
• Install cx_Oracle Driver:
# yum install -y cx_Oracle-5*
Verify cx_Oracle Installation
• Connect to the Python IDLE environment
• Type in the following commands:
>>> import cx_Oracle
>>> db = cx_Oracle.connect("student/student@xe")
>>> print db.version
• Returns the following for Oracle 11g XE:
11.2.0.2.0
Connect to Oracle
Implement a connect.py script
#!/usr/bin/python
# Import the Oracle library.
import cx_Oracle, sys
try:
# Create a connection.
db = cx_Oracle.connect("student/student@xe")
# Print a message.
print "Connected to the Oracle " + db.version + " database."
except cx_Oracle.DatabaseError, e:
error, = e.args
print >> sys.stderr, "Oracle-Error-Code:", error.code
print >> sys.stderr, "Oracle-Error-Message:", error.message
finally
# Close connection.
db.close();
Run a static SQL Statement
Implement a static query
#!/usr/bin/python
...
try:
# Create a connection.
db = cx_Oracle.connect("student/student@xe")
# Create a cursor.
cursor = db.cursor()
# Execute a query.
cursor.execute("SELECT 'Hello world!' FROM dual")
# Read the contents of the cursor.
for row in cursor:
print (row[0])
...
finally:
# Close cursor and connection.
cursor.close()
db.close()
Returning rows from a cursor
#!/usr/bin/python
...
# Execute a query.
cursor.execute("SELECT
",
"FROM
"WHERE
"
"
"
item_title " +
item_rating " +
item " +
item_type = ”
(SELECT common_lookup_id " +
FROM
common_lookup " +
WHERE common_lookup_type =
'DVD_WIDE_SCREEN')")
# Read the contents of the cursor.
for row in cursor:
print (row[0], row[1])
...
Run a dynamic SQL Statement
Binding a value in a cursor
The local variable.
#!/usr/bin/python
...
sRate = 'PG-13'
...
# Define a dynamic statment.
stmt = "SELECT item_title, item_rating " + \
"FROM item WHERE item_rating = :rating”
# Create a cursor.
The bind variable.
cursor = db.cursor()
# Execute a statement with a bind variable.
cursor.execute(stmt, rating = sRate)
# Read the contents of the cursor.
for row in cursor:
print (row[0], row[1])
Name and value
...
pair assignment.
Binding two values in a cursor
The list of local
variables.
#!/usr/bin/python
...
The bind variables.
# Define a list.
dvd = ('DVD_FULL_SCREEN','DVD_WIDE_SCREEN')|
...
stmt = "SELECT common_lookup_id"
+ "\n" + \
"FROM
common_lookup"
+ "\n" + \
"WHERE common_lookup_table = 'ITEM'"
+ "\n" + \
"AND
common_lookup_column = 'ITEM_TYPE'" + "\n" + \
"AND
common_lookup_type IN (:x,:y)”
# Parse the statement by replacing line returns with a single
# whitespace, replacing multiple whitespaces with single spaces.
stmt = re.sub('\s+',' ',stmt.replace('\n',' ').replace('\r',''))
# Declare a dynamic statement with a sequence.
cursor.execute(stmt, x = dvd[0], y = dvd[1])
...
Name and value
pair assignment.
Binding a dynamic dictionary
A tuple used to name dictionary
names, or the names of namevalue pairs.
#!/usr/bin/python
...
# Define an alphabetic indexing tuple.
ind = tuple('abcdefghijklmnopqrstuvwxyz')
# Define a parameter list and empty target list.
typ = ('DVD_FULL_SCREEN','DVD_WIDE_SCREEN','BLU-RAY')
mat = {}
...
Declaring an empty
dictionary.
A dynamic list of
variables that need to
bound to a dynamic SQL
statement
Binding a dynamic dictionary
Beginning of list of values.
...
# Define a dynamic query.
stmt = "SELECT common_lookup_id"
+ "\n" + \
...
"AND
common_lookup_column = 'ITEM_TYPE'" + "\n" + \
"AND
common_lookup_type IN ("
# Build dictionary and append dynamic bind list to statement.
for j, e in enumerate(typ):
mat[str(ind[j])] = typ[j]
if j == len(typ) - 1:
stmt = stmt + ":" + str(ind[j])
Logic to build list of
else:
bind variables and
stmt = stmt + ":" + str(ind[j]) + ", "
dynamic dictionary.
# Close lookup value set.
stmt = stmt + ")" + "\n" \
"ORDER BY 1”
...
Append closing
parenthesis of list.
Dynamic statement and dictionary
• Generated dynamic statement:
AND
common_lookup_column = 'ITEM_TYPE'
AND
common_lookup_type IN (:a, :b, :c)
ORDER BY 1
• Parse the query for line returns:
stmt = re.sub('\s+',' ',stmt.replace('\n',' ').replace('\r',''))
• Generated mat dictionary:
{'a': 'DVD_FULL_SCREEN', 'c': 'BLU-RAY', 'b': 'DVD_WIDE_SCREEN'}
• Call the query with a dictionary:
cursor.execute(stmt, mat)
Binding a transaction
...
# Declare variables.
sItemTitle = 'Star Trek Beyond’
sItemSubtitle = 'Extended Edition'
...
# Execute a query.
stmt = "UPDATE item"
+ "\n" + \
"SET
item_subtitle = :bItemSubtitle" + "\n" + \
"WHERE item_title = :bItemTitle"
...
# Declare a dynamic statement.
cursor.execute(stmt, bItemTitle = sItemTitle
, bItemSubtitle = sItemSubtitle )
# Commit the inserted value.
db.commit()
...
Assign local variables
Commit change.
to bind targets.
Transaction Control
• You start a transaction like:
# Set a starting transaction point.
db.begin()
• Commit the write in the try-block:
db.commit()
• Rollback in the except block with an error:
db.rollback()
Call PL/SQL stored programs
Calling a procedure
...
# Create a connection.
db = cx_Oracle.connect("student/student@xe")
First call parameter
# Create a cursor.
is the name of the
cursor = db.cursor()
procedure.
# Call a stored procedure.
cursor.callproc( 'insert_bill_detail' \
, ( sBillNumber
\
Second call parameter is
, sBillText
\
the list of actual
, sDetailNumber \
parameters.
, sDetailText ))
...
Calling a procedure with list
A parameter list.
...
# Create a sequence for a procedure call.
param = (sBillNumber, sBillText, sDetailNumber, sDetailText)
try:
# Create a connection.
db = cx_Oracle.connect("student/student@xe”
# Create a cursor.
cursor = db.cursor()
# Call a stored procedure.
cursor.callproc( 'insert_bill_detail', param)
...
Call parameters bundled
in a list.
Calling a function with list
...
# Create a sequence for a procedure call.
param = (sBillNumber, sBillText, sDetailNumber, sDetailText)
try:
# Create a connection.
Function return type.
db = cx_Oracle.connect("student/student@xe")
# Create a cursor.
cursor = db.cursor()
# Call a stored procedure.
fRetVal = cursor.callfunc( 'insert_bill_detail_func', cx_Oracle.NUMBER, param)
# Check for successful function call or failure number.
if fRetVal == 0:
print "Success”
else:
print "Failure [" + str(int(fRetVal)) + "]”
...
Capture a failure code
from the function.
Review
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Introduce Python
Learn how to install cx_Oracle
Learn how to connect to Oracle
Learn how to run static SQL statements
Learn how to run dynamic SQL statements
Learn how to call PL/SQL store programs
Questions & Answers