Python database connection
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This document discusses connecting to a PostgresSQL database using the Psycopg2 library in Python. It provides steps for installing Psycopg2, connecting to an existing database, executing commands like creating a table, querying the database, and retrieving data. Functions for connecting, creating cursors, committing transactions, and closing connections are also overviewed. An example Python code snippet demonstrates importing Psycopg2, connecting to a database, executing a query, fetching the results, and closing the connection.
Python database connection
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- 3. Python database connection: Shameena v [email protected] www.facebook.com/shamee navayoli twitter.com/username in.linkedin.com/in/shamean 9567135569
- 4. Introduction • Psycopg2 is the most popular PostgreSql adapter for the Python programming language • core it fully implements the pythondb API 2.0 • Install the Psycopg2 Command for installation: • sudo apt-get install python-psycopg2 Creating user Here we install the psycopg2 module on a Ubuntu system. $ sudo -u postgres createuser janbodnar Shall the new role be a superuser? (y/n) y
- 5. Steps: 1) We want to import psycopg2 in code Import psycopg2 2) Connect to an existing database conn = psycopg2.connect("dbname=test user=postgres") cur=conn.cursor() 3) Execute a command: this creates a new table cur.execute("CREATE TABLE test (id serial PRIMARY KEY, num integer, data varchar);")
- 6. • Query the database and obtain data as Python objects cur.execute("SELECT * FROM test;") cur.fetchone() (1, 100, "abc'def") 4) Make the changes to the database persistent conn.commit() 5) Close communication with the database conn.close()
- 7. • The function connect() creates a new database session and returns a new connection instance. • The class connection encapsulates a database session. It allows to: create new cursor using the cursor()method to execute database commands and queries, terminate transactions using the methods commit()or rollback()
- 8. . • The class cursor allows interaction with the database: ---send commands to the database using methods such as execute() and executemany() ---retrieve data from the database by iteration or using methods such as fetchone(), fetchmany(), fetchall().
- 9. Example: import psycopg2 try: con=psycopg2.connect("dbname = testdb user = shafeequemonp'") cur=con.cursor() cur.execute('SELECT version()') ver=cur.fetchone() print ver except psycopg2.DatabaseError.e: print 'Error %s' % e sys.exit(1) finally: if con: con.close()
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