Connect to a PostgreSQL database(python).

#python #database #postgres #webdev

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 ```bash

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 
![Img](https://media.geeksforgeeks.org/wp-content/uploads/20220822143634/pgadmin4CreatingaDatabase.png)
- 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;

![img](https://media.geeksforgeeks.org/wp-content/uploads/20220822174010/Createdatabaseusingcomand.jpg)
## Connecting to the database
We need to connect to a PostgreSQL database using psycopg2.connect() function.
**Where the attributes of connect() function are:**
```python


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: ```python

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.
```python


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.')

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