# Django Basics

> <https://developer.mozilla.org/en-US/docs/Learn/Server-side/Django/Introduction>

\ <br>

### What is django?

: Python web framework

* High-level Python web framework that enables rapid development of **secure** and **maintainable** websites
* Free & open source

<br>

#### web framework

* Aims to reduce difficulties encountered in web page development process
* A collection of classes and libraries that implement the standard structure of applications

<br>

#### Why do we have to learn django?

1. `Portable`
   * Python based which means it runs on many platforms
2. `Complete`
   * **Django** follows the *"Batteries included"* philosophy
     * Everything you need is part of the one *"product"*
     * Works seamlessly together
     * Follows consistent design principles
     * Has extensive and [up-to-date documentation](https://docs.djangoproject.com/en/stable/).
3. `Versatile`
   * Can be used to build almost any type of website
     * Can work with any **client-side** framework
     * Can deliver content in almost any format (including HTML, RSS feeds, JSON, XML, etc)
4. `Secure`
   * Provides a secure way to manage user accounts & passwords
     * By avoiding common mistakes like putting session information in cookies where it is vulnerable
       * Instead cookies just contain a key
       * And the actual data is stored in the db
     * By avoiding directly store passwords rather than **password hash**
5. `Scalable`
   * Uses a component-based *"shared-nothing"* architecture
     * each part of the architecture is independent of the others
     * can be replaced or changed if needed
   * Can scale for increase traffic by adding hardware at any level
     * caching servers
     * database servers
     * application servers
6. `Maintainable`
   * Follows DRY (Don't Repeat Yourself) principle
     * No unnecessary duplication
   * Promotes the grouping of related functionality into reusable
7. Many companies are utilizing it
   * Spotify
   * Instagram
   * Dropbox
   * Delivery Hero
   * etc.

\ <br>

#### Web protocol we know

* Request
* Response

\ <br>

### How does django work?

* Django follows the **MVC (Model View Controller) pattern**.
  * MVC: One of the Software design patterns

    | MVC Pattern |  django  |
    | :---------: | :------: |
    |    Model    |   Model  |
    |     View    | Template |
    |  Controller |   View   |
* **MTV**
  * **M**: Data management
  * **T**: Interface (screen)
  * **V**: Intermediate management (interaction)

![img](https://mdn.mozillademos.org/files/13931/basic-django.png)

\ <br>

### Run django on CS 50 IDE

<br>

#### CS 50 IDE

: CS50 IDE is a **cloud-based** Integrated Development Environment powered by [**AWS Cloud9**](https://aws.amazon.com/cloud9/) that features a cloud-based Ubuntu environment, a browser-based editor that supports syntax highlighting and word completion, a GUI-based GDB debugging, themes, customizable layouts, keyboard shortcuts, and many more features. Since it's cloud-based, you can continue working on your problem sets even if you use a different computer!

<br>

#### AWS Cloud 9

> Cloud-based IDE (Integrated Development Environment)

* OS: Ubuntu 18.04.4 LTS
  * python 3.7.6
* Advantage of not affecting the local development environment

<br>

![image-20200326100727731](https://199941116-files.gitbook.io/~/files/v0/b/gitbook-legacy-files/o/assets%2F-M6ivT9AfNVmiT1Q6B2U%2Fsync%2F6c436d5f3cc0d27509c5aef99a315443c127fa67.png?generation=1588852096323830\&alt=media)

<br>

#### Django installation

```shell
$ pip install django==2.1.15
```

* Download version 2.1.15

<br>

#### Django uninstall

```shell
$ pip uninstall django
```

<br>

#### Create project

```shell
$ django-admin startproject {project name}
```

<br>

#### Run server

* Edit line 28 of settings.py

```python
ALLOWED_HOSTS = ['*']
```

<br>

* Always check the directory where the command is executed when running the server

```shell
$ cd djanggo_intro/
$ ls
$ python manage.py runserver 8080
```

* For the running server, click the URL in the right area

  ![image-20200326102907761](https://199941116-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M6ivT9AfNVmiT1Q6B2U%2Fuploads%2Fgit-blob-0a6651949db811f7dcb9667f25c07ccf9ceb686c%2Fimage-20200326102907761.png?alt=media)
* To stop the server, use `ctrl + c` in terminal

<br>

> Server running screen

![image-20200326102049790](https://199941116-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M6ivT9AfNVmiT1Q6B2U%2Fuploads%2Fgit-blob-baf82853fbba21b1e52caa1ed9fcca720da111b6%2Fimage-20200326102049790.png?alt=media)

\ <br>

#### Create app

```shell
$ python manage.py startapp pages
```

\ <br>

#### Start Project

```shell
$ django-admin startproject first_django
```

* `project` is the *atomic* unit of Django!

<br>

#### Created project folder structure

<br>

![image-20200326122807719](https://199941116-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M6ivT9AfNVmiT1Q6B2U%2Fuploads%2Fgit-blob-31ac96f2e25b3949c9d3143ccec727528f1d6269%2Fimage-20200326122807719.png?alt=media)

<br>

#### Create Pages

```shell
$ python manage.py startapp pages
```

#### Git

```shell
$ git init
$ ls -al
$ rm -rf .git
```

#### `INSTALLED_APPS`

: Registration

![image-20200326131656480](https://199941116-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M6ivT9AfNVmiT1Q6B2U%2Fuploads%2Fgit-blob-ff9742ce6c26f27e71e05260438a9003f3c4e2cb%2Fimage-20200326131656480.png?alt=media)

* Added `pages` for registration

<br>

#### Start Server

```shell
$ python manage.py runserver 8080
```

<br>

![image-20200326124046226](https://199941116-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-M6ivT9AfNVmiT1Q6B2U%2Fuploads%2Fgit-blob-a10ba54541f8c013123feac91318a6ada4aad3a9%2Fimage-20200326124046226.png?alt=media)

<br>

#### Check Port Number

```shell
$ echo $PORT
8080
```

* Can confirm connection to ports 80 and 8080

<br>

#### Check IP

```shell
$ echo $IP
127.0.0.1
```

<br>

*Django has `DEBUG=True` as default*

\ <br>

### urls.py

> Gatekeeper

```python
from django.contrib import admin
from django.urls import path

urlpatterns = [
    path('request URL/', handling view(controller) function)
    path('admin/', admin.site.urls),
]
```

* `path('request URL/', handling view(controller) function)`
  * Django's characteristic is that URLs end with `/`!

<br>

### pages/views.py

```python
from django.shortcuts import render

# Create your views here.

def hello():
    return render(request,'HTML file name')
```

* Every time hello() is called, the object that called the function enters as the first argument
  * When defining a function in view, always define the first argument as `request`!

```python
def lotto(request):
    import random
    pick = random.sample(range(1,46),6)
    context = {'pick':pick}
    return render(request, 'lotto.html', context)
```

* First argument - `request`
* Second argument - file name
* Third argument - context
  * Context must always be a **dictionary**!

<br>

### Create pages/templates folder

* The name must be `templates`

<br>

#### Kill running python files

```shell
$ killall python
$ killall python3
```

\ <br>

## Wrap-up

<br>

### App Creation

* Django consists of one project with multiple apps
  * ex) Creating a community
    * App related to members - `accounts`
    * App related to posts - `posts`

```shell
$ python manage.py startapp {app name}
```

* After creating an app, must register it in `INSTALLED_APPS` in `settings.py`

  ```python
  INSTALLED_APPS = [
      ...
      'pages',
  ]
  ```

\ <br>

### Basic Flow

<br>

#### 1. URL Configuration

* `urls.py`

  ```python
  # django_intro/urls.py
  from pages import views

  urlpatterns = [
      path('lotto/', views.lotto),
  ]
  ```

  * URLs in path are always closed with `/`

  <br>

#### 2. View Configuration

* `views.py`

  ```python
  # pages/views.py

  import random
  def lotto(request):
      pick = random.sample(range(1,46),6)
      context = {
          'pick': pick
      }
      return render(request, 'lotto.html', context)
  ```
* When defining functions, always write the first argument as `request`
  * Why? Because internally when processing requests, it needs to send an object containing request information when calling functions
* Return through `render` function
  * First argument: `request`
  * Second argument: template file (`html`)
  * Third argument
    * dictionary type
    * Pass values to be used in template

<br>

#### 3. Create `templates` file

* The `html` file to return is always created inside the `templates` folder


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