> For the complete documentation index, see [llms.txt](https://pyohamen.gitbook.io/til/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://pyohamen.gitbook.io/til/django/01_django101.md).

# Intro to Django

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

### What is django?

: Python web framework

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

#### web framework

* web page 개발하는 과정에서 겪는 어려움을 줄이는 것이 목적
* 응용 프로그램의 표준 구조 를 구현하는 class와 library의 목록

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

1. `Portable`
   * Python based which means it  runs on may platform
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. 많은 기업에서 활용중
   * Spotify
   * Instagram
   * Dropbox
   * Delivery Hero
   * etc.

#### 우리가 알고 있는 web 의 protocol

* 요청 (request)
* 응답 (response)

### django 는 어떻게 (how) 동작하는가?

* django는 **MVC (Model View Controller) pattern** 을 따르고 있다.
  * MVC: Software design pattern 중 하나

    | MVC Pattern |  django  |
    | :---------: | :------: |
    |    Model    |   Model  |
    |     View    | Template |
    |  Controller |   View   |
* **MTV**
  * **M**: 데이터 관리
  * **T**: 인터페이스 (화면)
  * **V**: 중간 관리 (상호 동작)

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

### Run django on CS 50 IDE

#### 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!

#### AWS Cloud 9

> Cloud 기반 IDE (통합 개발 환경)

* OS: Ubuntu 18.04.4 LTS
  * python 3.7.6
* 개발 local 환경에 영향이 없다는 장점이 있음

![image-20200326100727731](https://github.com/pyohamen/TIL/tree/c406d6f5d12dcc8f41be5a252583f3ed8e46c4a3/images/image-20200326100727731.png)

#### django 설치

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

* 2.1.15 로 다운받기

#### django uninstall

```
$ pip uninstall django
```

#### 프로젝트 생성

```
$ django-admin startproject {프로젝트 명}
```

#### 서버 실행

* settings.py 28 번째 줄 수정하기

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

* 서버 실행 시 반드시 명령어가 실행되는 directory를 확인 할 것

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

* 실행된 서버는 우측 영역의 url을 click한다

  ![image-20200326102907761](https://github.com/pyohamen/TIL/tree/c406d6f5d12dcc8f41be5a252583f3ed8e46c4a3/images/image-20200326102907761.png)
* 서버 종료는 terminal에서 `ctrl + c`

> 서버 실행 된 화면

![image-20200326102049790](https://github.com/pyohamen/TIL/tree/c406d6f5d12dcc8f41be5a252583f3ed8e46c4a3/images/image-20200326102049790.png)

#### app 만들기

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

#### Project 시작하기

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

* `project` 는 django의 *atomic* 한 단위!

#### 생성된 project folder 구조

![image-20200326122807719](https://github.com/pyohamen/TIL/tree/c406d6f5d12dcc8f41be5a252583f3ed8e46c4a3/images/image-20200326122807719.png)

#### Pages 만들기

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

#### Git

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

#### `INSTALLED_APPS`

: 주민등록

![image-20200326131656480](https://github.com/pyohamen/TIL/tree/c406d6f5d12dcc8f41be5a252583f3ed8e46c4a3/images/image-20200326131656480.png)

* 주민등록을 위해 `pages` 추가함

#### Server 가동

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

![image-20200326124046226](https://github.com/pyohamen/TIL/tree/c406d6f5d12dcc8f41be5a252583f3ed8e46c4a3/images/image-20200326124046226.png)

#### Port 번호 확인

```
$ echo $PORT
8080
```

* 80번과 8080으로 연결되어 있는 것 확인 가능

#### IP 확인

```
$ echo $IP
127.0.0.1
```

*django는 `DEBUG=True` 가 default*

### urls.py

> 문지기

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

urlpatterns = [
    path('요청 URL/', handling 할 view(controller) 함수)
    path('admin/', admin.site.urls),
]
```

* `path('요청 URL/', handling 할 view(controller) 함수)`
  * url 끝에 `/` 가 붙는게 django의 특징!

### pages/views.py

```python
from django.shortcuts import render

# Create your views here.

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

* hello() 가 불릴 때마다 함수를 부른 객체가 첫번째 인자로 들어감
  * view에서 함수를 정의하는 경우 항상 첫번째 인자를 `request`로 정의한다!

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

* 첫 번째 인자 - `request`
* 두 번째 인자 - 파일 명
* 세 번째 인자 - context
  * context는 항상 **dictionary** 로 해야함!

### pages/templates folder 만들기

* 이름이 꼭 `templates` 여야 한다

#### 돌고있는 python 파일 죽이기

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

## Wrap-up

### App 생성

* django는 여러개의 앱을 가진 하나의 project로 구성된다
  * ex) 커뮤니티를 만든다
    * 회원과 관련된 app - `accounts`
    * 게시글과 관련된 app - `posts`

```
$ python manage.py startapp {app 이름}
```

* app을 생성하고 반드시 `settings.py`의 `INSTALLED_APPS`에 등록한다

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

### 기본 흐름

#### 1. URL 지정

* `url.py`

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

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

  * path 에 url은 항상 `/` 로 닫아준다

#### 2. view 지정

* `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)
  ```
* 함수를 정의할 때, 항상 첫번 째 인자는 `request`로 작성해둔다
  * why? 내부적으로 요청을 처리 할 때, 함수 호출 시 요청 정보가 담긴 객체를 보내줘야 해서
* `render` 함수를 통해서 반환한다
  * 첫번째 인자: `reqeust`
  * 두 번째 인자: template file (`html`)
  * 세번째 인자
    * dictionary type
    * template에서 활용 하려고 하는 값들을 전달

#### 3. `templates` 파일 생성

* 반환할 `html` file은 항상 `templates` folder 안에 생성한다

  ```markup
  <!-- pages/templates/lotto.html -->
  <p>
      {{pick}}
  </p>
  ```

  * context dictionary의 key 값을 적으면 출력된다


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