Connect python application with postgreSQL database using psycopg2. Perform DDL & DML operations Create table , Insert/update/delete and select records Understand connection & cursor class

1. PostgreSQL Python
1. psycopg2-binary : PostgreSQL Adaptor
2.DDL Operations
3.DML Operations

2. Installation
 pip install psycopg2-binary
 pip3 install psycopg2-binary

3. Python Connectors
Python
Application
pymongo
sqlite3
mySQL
pyscopg2
Python Module/Connector
Python DB API’s
Request
Response

4. Steps
1) Create Connection string
2) Open connection
3) Open cursor
4) Execute cursor
5) Close Cursor
6) Close Connection

5. Connection
Connection class
 Handles connection to database instances
 Encapsulates a database session
Connection String Example
psycopg2.connect(database="sample",user="postgres",password="sample",
host="127.0.0.1", port="5432")
connection.cursor( )
creates a cursor which will be used throughout of your database programming
with Python

6. Connection Method ( )
connection.commit ( )
 Commits the current transaction
 Changes will not reflect to other connections if not commited
 Default, psycopg opens a transaction before executing the first command
connection.rollback( )
 This method rolls back any changes to the database since the last call to
commit( )
connection.close( )
 This Method closes the database connection.
 If you close your database connection without calling commit() first, your
changes will
be lost!

7. CURSOR
 Cursor is Class
 Allows Python code to execute PostgreSQL
command in a database session
 Created by
 connection.cursor( ) Method
 cursor.execute( ), cursor.fetch( ),cursor.close( )

8. Execute( )
cursor.execute (query [, optional parameters])
 Execute a database operation (query or command)
returns None.
 Cursor.execute(“select * from test”)
 The returned values can be retrieved using fetch*( )
methods
cursor.executemany(query, vars_list)
 Execute a database operation (query or command)
against all parameter tuples or mappings found in
the sequence vars_list

9. Call Procedures
 cursor.callproc(procname[, parameters])
- Call database stored procedure
- The sequence of parameters must contain one entry for
each argument that the procedure expects
- Overloaded procedure supported
- The procedure may provide a result set as output.
- This is then made available through the standard fetch*()
methods

10. Fetch()
 cursor.fetchone( )
- Fetch the next row of a query result set, returning a single tuple
 cursor.fetchall( )
- This routine fetches all (remaining) rows of a query result, returning a
list. An empty list is returned when no rows are available.
 cursor.fetchmany([size=cursor.arraysize])
- Fetch the next set of rows of a query result, returning a list of
tuples.An empty list is returned when no more rows are available.

11. Cursor.*
Cursor.rowcount
This read-only attribute which returns the total number of database rows that
have been modified, inserted, or deleted by the last last execute*().
Cursor.query
Returns last executed query

12. DDL/DML OPERATIONS
-- Create Table
-- Drop Table
-- Insert Record
-- Update Record
-- Select Record
-- Delete Record

13. List Database
#Import library
import psycopg2
#Open Connection
conn = psycopg2.connect(database="postgres",
user='postgres', password='postgres',
host='127.0.0.1', port= '5432')
#Open cursor
cursor = conn.cursor()
#Execute Cursor
cursor.execute("select datname from

14. Select
import psycopg2
conn = psycopg2.connect(database = "postgres",
user = "postgres", password = "postgres", host =
"127.0.0.1", port = "5432")
cursor = conn.cursor()
cursor.execute("select * from test2")
data = cursor.fetchone()
cursor.execute("select * from test2")
data = cursor.fetchmany(2)

15. Create Table
import psycopg2
conn = psycopg2.connect(database =
"postgres", user = "postgres", password =
"postgres", host = "127.0.0.1", port =
"5432")
print ("Opened database successfully")
cur = conn.cursor()
cur.execute('''CREATE TABLE COMPS
(ID INT PRIMARY KEY NOT NULL,

16. Insert
#CREATE TABLE
- cursor.execute("CREATE TABLE test (id serial PRIMARY KEY, num integer,
data varchar(99));")
- conn.commit
#INSERT/UPDATE RECORD
cursor.execute("INSERT INTO test (num, data) VALUES (%s, %s)",(100,
"sqlnosql.com"))
conn.commit
#UPDATE
cursor.execute("UPDATE test2 set num = 999 where ID = 4")
conn.commit
cursor.rowcount

17. Python file
Write code in python file
Vi a.py
#Execute
python3 a.py

18. Contact
Website: www.sqlnosql.com
Email : sachinep84@gmail.com
Linkedin : https://www.linkedin.com/in/sachinep84/