Django Knowledgebase

Installation

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pip install django

Commands

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django-admin startproject <project-name> - Create a Django project

python manage.py runserver - Run the Django dev server

python manage.py makemigrations - Create Migration Scripts

python manage.py migrate - Migrate Database

File Structure

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    project-name/                  ← higher level folder
    |-- project-name/             ← django project folder
    |    |-- project-name/
    |    |    |-- init.py
    |    |    |-- settings.py
    |    |    |-- urls.py
    |    |    |-- wsgi.py
    |    +-- manage.py

Five main files of the base project are as follows:

manage.py - Used to run management commands related to the project [migrations, run server, etc]

init.py - Empty file to indicate Python that this is a package

settings.py - Whole projects configuration file

urls.py - Maps all the requests to the routes/paths

wsgi.py - Used for deployment

A Django project can have multiple apps for different functionalities in it.

In this file tree, we have created an app called sampleapp

    project-name/
    |-- project-name/
    |    |-- sampleapp/                <-- our new django app!
    |    |    |-- migrations/
    |    |    |    +-- __init__.py
    |    |    |-- __init__.py
    |    |    |-- admin.py
    |    |    |-- apps.py
    |    |    |-- models.py
    |    |    |-- tests.py
    |    |    +-- views.py
    |    |-- project-name/
    |    |    |-- __init__.py
    |    |    |-- settings.py
    |    |    |-- urls.py
    |    |    |-- wsgi.py
    |    +-- manage.py

Creating Databse in PostgreSQL

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createdb -U {{username}} -h localhost --owner={{username}}--lc-ctype='en_US.UTF-8' --lc-collate='en_US.UTF-8' --encoding='UTF8' -e {{db name}};

Copying Database in PostgreSQL

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CREATE DATABASE {{new_db}} WITH TEMPLATE {{original_db}} OWNER {{username}};

Dropping Database in PostgreSQL

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dropdb -U {{username}} -h localhost {{db_name}};

Adding Table in PostgreSQL

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ALTER TABLE table_name
ADD COLUMN new_column_name data_type;

Copy Data from one column to another

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UPDATE {{table_name}} 
SET {{column1}} = {{column2}}

Dropping Table in PostgreSQL

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DROP TABLE {{table_name}};

Dropping Column in PostgreSQL

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ALTER TABLE {{table_name}} 
DROP COLUMN {{column_name}};

Import CSV File Into PosgreSQL Table

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Example

CREATE TABLE persons
(
  id serial NOT NULL,
  first_name character varying(50),
  last_name character varying(50),
  dob date,
  email character varying(255),
  CONSTRAINT persons_pkey PRIMARY KEY (id)
)

Change DB to Postgres

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In your projects setting.py, change the following

. . .

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': os.path.join(BASE_DIR, 'db.sqlite3'),
    }
}
. . .

to

. . .

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.postgresql_psycopg2',
        'NAME': '{{db name}}',
        'USER': '{{username}}',
        'PASSWORD': '{{password}}',
        'HOST': 'localhost',
        'PORT': '', # Leave it empty to use default - 5432
    }
}
. . .

After changing the backend,

python manage.py makemigrations - Create the migration scripts

python manage.py migrate - Run the migration scripts

Creating Python Virtual Environment

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python3 -m venv /path/for/virtual/environment