connecting to a PostgreSQL database from Python.

Installation:

• Install PostgreSQL, If you haven’t installed it.
• We need to install the psycopg2 library to connect to a PostgreSQL database. Open the command prompt and run the below command to install psycopg2

pip3 install psycopg2

Creating a Database

You can create a Database in 2 Ways:

1. Using pgAdmin 4 UI
2. Using command

1. Using pgAdmin 4 UI
Go to pgAdmin and Follow these Steps.

• Local_server[Right Click] -> Create -> Database
• Next, Fill out the form Database: WorkSpace and Save.

2. Create Database Using SQL query
Go to pgAdmin and follow these Steps:

• Run the below Command in the Query tab

CREATE DATABASE WorkSpace;

Connecting to the database

We need to connect to a PostgreSQL database using psycopg2.connect() function.
Where the attributes of connect() function are:

host = hostname,
dbname = databaseName,
user = username,
password = [Your Password],
port = [port_id]

In case you don’t know any of these connect() function attributes, you can follow the below steps:


Now You Know All the properties of this Database. Let’s continue.

Now, to connect to the database, we need to pass the attributes as arguments to the connect() function.

Syntax:

conn = psycopg2.connect(
    host = 'localhost',
    dbname = 'For_Practice',
    user = 'postgres',
    password = '[Password]',
    port = 5432
)

Create a cursor:

• Create a cursor(i.e., curr) object and call its execute() method to execute queries.
• Where execute() method is used to run a query that is passed as a string. Syntax:

cur = conn.cursor()
cur.execute('[SQL queries]')

In the end, We need to save the changes using commit() method and finally close the opened connection using close() method.

conn.commit()
cur.close()

import psycopg2

conn = None
try:
    # connect to the PostgreSQL server
    print('Connecting to the PostgreSQL database...')
    conn = psycopg2.connect(
        host = 'localhost',
        dbname = 'For_Practice',
        user = 'postgres',
        password = '321654',
        port = 5432
    )

    # Creating a cursor with name cur.
    cur = conn.cursor()
    print('Connected to the PostgreSQL database')

    # Execute a query:
    # To display the PostgreSQL
    # database server version
    cur.execute('SELECT version()')
    print(cur.fetchone())

    # Close the connection
    cur.close()

except(Exception, psycopg2.DatabaseError) as error:
    print(error)
finally:
    if conn is not None:
        conn.close()
        print('Database connection closed.')