Flask-development

In this repository, I will to learn how to use Flask and with those framework React.Js for Frontend development.

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1. Basics of Flask

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1. Basics of Flask

Install Flask

"Hello, World" in Flask

Routes and Contecst

Generators and Iterators

Postgresql - install on ubuntu

Open Terminal and then follow these steps:

sudo apt update sudo apt install postgresql postgresql-contrib

• sudo systemctl status postgresql - for check status on server

• sudo systemctl stop postgresql - for stop server

• sudo systemctl start postgresql - start server

• sudo systemctl restart postgresql - restart server

Next, let’s try to login to the PostgreSQL console. First, we need to switch to postgres user:

dhani@dhani-virtual-machine:~$ sudo -i -u postgres postgres@dhani-virtual-machine:~$

Now use the psql command to enter the console

postgres@dhani-virtual-machine:~$ psql psql (11.5 (Ubuntu 11.5-1)) Type "help" for help. postgres=#

To quit from the console, type: \q

By default, the postgres user does not have a password. So, let’s create a new one.

Create or change postgres user password

To change postgres user or any other user, use the following syntax. For example:

ALTER ROLE postgres WITH PASSWORD '12345';

The command will change the postgres user password to 12345.

Install PgAdmin on Ubuntu 19.10

PgAdmin is a free, web-based administration tool for PostgreSQL database. It is a handy, rich features tool that you will love. You can use PgAdmin to create a new database, manage users, and do many other things. To install PgAdmin on Ubuntu 19.10, follow these steps.

Step 1. Install Prerequisites

Open Terminal and paste the following commands

sudo apt-get install curl ca-certificates gnupg curl https://www.postgresql.org/media/keys/ACCC4CF8.asc | sudo apt-key add -

Step 2. Create a new repo file

Create a new file eoan-pgdg.list inside /etc/apt/sources.list.d directory and then paste the following line into the new file

deb http://apt.postgresql.org/pub/repos/apt/ eoan-pgdg main

Step 3. Update and Install PgAdmin

Now we are ready to install PgAdmin.

sudo apt update sudo apt install pgadmin4

After that, you should see the PgAdmin4 application icon in the Ubuntu application list.

How to enable Remote access to the PostgreSQL Server

It is important to make sure the user can connect to the PostgreSQL server from the network. There are some steps we need to take to enable the network access to the server.

Edit the pg_hba.conf

sudo nano /etc/postgresql/12/main# nano pg_hba.conf

Add the following lines to the end of the file

host all all 0.0.0.0/0 md5 host all all ::0 md5

Close and save the file. And then restart PostgreSQL Service

sudo systemctl restart postgresql

Edit the postgresql.conf

We also need to edit the postgresql.conf file.

sudo nano /etc/postgresql/12/main/postgresql.conf

Find the following line

#listen_addresses = 'localhost'

And then change it to listen_addresses = '*'

Close and save the file and restart the service sudo systemctl restart postgresql

Done. Now try to connect to the PostgreSQL Server from the network. You should now able to connect.