PostgreSQL provides its own shell to execute queries. To establish connection with the PostgreSQL database, make sure that you have installed it properly in your system. Open the PostgreSQL shell prompt and pass details like Server, Database, username, and password. If all the details you have given are appropriate, a connection is established with PostgreSQL database.

While passing the details you can go with the default server, database, port and, user name suggested by the shell.

Establishing Connection Using Python

The connection class of the psycopg2 represents/handles an instance of a connection. You can create new connections using the connect() function. This accepts the basic connection parameters such as dbname, user, password, host, port and returns a connection object. Using this function, you can establish a connection with the PostgreSQL.

Example

The following Python code shows how to connect to an existing database. If the database does not exist, then it will be created and finally a database object will be returned. The name of the default database of PostgreSQL is postrgre. Therefore, we are supplying it as the database name.

import psycopg2
#establishing the connection
conn = psycopg2.connect(
   database="postgres", user=''postgres'', password=''password'', 
   host=''127.0.0.1'', port= ''5432''
)

#Creating a cursor object using the cursor() method
cursor = conn.cursor()

#Executing an MYSQL function using the execute() method
cursor.execute("select version()")

#Fetch a single row using fetchone() method.
data = cursor.fetchone()
print("Connection established to: ",data)

#Closing the connection
conn.close()
Connection established to: (
   ''PostgreSQL 11.5, compiled by Visual C++ build 1914, 64-bit'',
)

Output

Connection established to: (
   ''PostgreSQL 11.5, compiled by Visual C++ build 1914, 64-bit'',
)