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[Django] - part1.2: Official Docs Note

「Django」part1.2: (EN)
 2021/python/django

「Django」part1.2: Official Docs Note(EN)

關於 Django 的官方文件筆記(EN)，紀錄起來，讓自己可以快速統整 👐

關於 Django 的官方文件筆記(EN)

< Intro >

"A popular python web framework ! " ----> Django Docs

< Quick Start >

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pip install Django

1. Create Django Project

django-admin startproject mysite

2. Run locally

http://127.0.0.1:8000/

cd mysite
python manage.py runserver
  • Changing the port
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# http://127.0.0.1:8080/
python manage.py runserver 8080

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# http://0.0.0.0:8000/
python manage.py runserver 0:8000

< Create App >

1. Create App polls

Under the same path with manage.py

python manage.py startapp polls

2. Write first View in App

In the polls/views.py

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from django.shortcuts import render

# Create your views here.
from django.http import HttpResponse

def index(request):
    return HttpResponse("Hello, world. You're at the polls index.")

3. Create URLconf to configure urlpatterns in polls

  • Under polls/
  • Create urls.py

In the polls/urls.py

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from django.urls import path

from . import views

urlpatterns = [
    path('', views.index, name='index'),
]

4. Point the root URLconf at polls.urls module ( Setting in mysite/urls.py )

In the mysite/urls.py

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from django.contrib import admin
from django.urls import path, include

urlpatterns = [
    path('admin/', admin.site.urls),
    path('polls/', include('polls.urls')),
]

5. Run locally to see polls/

http://localhost:8000/polls/

python manage.py runserver

< DB Setup >

- Creates db table

python manage.py migrate

This command looks at the INSTALLED_APPS setting and creates any necessary database tables according to the database settings in mysite/settings.py and the database migrations shipped with the app.

- Creating models

In the polls/models.py

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from django.db import models

# Create your models here.
class Question(models.Model):
    question_text = models.CharField(max_length=200)
    pub_date = models.DateTimeField('date published')


class Choice(models.Model):
    question = models.ForeignKey(Question, on_delete=models.CASCADE)
    choice_text = models.CharField(max_length=200)
    votes = models.IntegerField(default=0)

- Activating models

We need to include app in project, so we need to reference to its configuration class in the mysite/settings.py

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INSTALLED_APPS = [
    'polls.apps.PollsConfig',
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
]

But why is polls.apps.PollsConfig, it's because polls configuration file is in polls/apps.py and the Class is called PollsConfig, so we need to write polls.apps.PollsConfig.

- Make migrations

python manage.py makemigrations polls
  • Telling Django that you’ve made some changes to your models and that you’d like the changes to be stored as a migration.
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# You will see somthing like this.
Migrations for 'polls':
  polls/migrations/0001_initial.py
    - Create model Question
    - Create model Choice

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# And migrations folder

- Get the Raw SQL for the migration you give.

python manage.py sqlmigrate polls 0001

- Check for any problems in project

python manage.py check

- Create model tables in daatbase:

So run migrate again.

python manage.py migrate

< So, Basic Migrate Workflow is:>

  1. Change models in models.py
  2. Activate models in INSTALLED_APPS
  3. python manage.py makemigrations to create migrations for new changes.
  4. python manage.py migrate to apply changes to the database.

< Django python shell >

- Run this command to enter:

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python manage.py shell

- Can use django framework to edit project, add some change in database here.

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>>> from polls.models import Choice, Question
>>> Question.objects.all()
# <QuerySet []>
>>> from django.utils import timezone
>>> q = Question(question_text="What's new?", pub_date=timezone.now())

>>> q.save()
>>> q.id
>>> q.question_text
# "What's new?"
>>> q.pub_date
# datetime.datetime(2012, 2, 26, 13, 0, 0, 775217, tzinfo=<UTC>)
>>> q.question_text = "What's up?"
>>> q.save()
>>> q.question_text
# "What's up?"
>>> Question.objects.all()
# <QuerySet [<Question: Question object (1)>]>

Because usually we don't want Question.objects.all() to show <QuerySet [<Question: Question object (1)>]> for us, we want more clear infos for the model object we choose, so we can add __str__() in models.py class

- Adding __str__() method to both Question and Choice in polls/models.py

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import datetime

from django.db import models
from django.utils import timezone


# Here we just return text
class Question(models.Model):
    # ...
    def __str__(self):
        return self.question_text
    
    def was_published_recently(self):
        return self.pub_date >= timezone.now() - datetime.timedelta(days=1)

class Choice(models.Model):
    # ...
    def __str__(self):
        return self.choice_text

- Testing and playing around with shell again:

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python manage.py shell

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>>> from polls.models import Choice, Question
>>> Question.objects.all()
# <QuerySet [<Question: What's up?>]>
# So now we can see the clear info for what we choose

>>> Question.objects.filter(id=1)
# <QuerySet [<Question: What's up?>]>


>>> Question.objects.filter(question_text__startswith='What')
# <QuerySet [<Question: What's up?>]>


>>> from django.utils import timezone
>>> current_year = timezone.now().year
>>> Question.objects.get(pub_date__year=current_year)
# <Question: What's up?>


>>> Question.objects.get(pk=1)
# pk is primary key
# <Question: What's up?>
>>> q = Question.objects.get(pk=1)
>>> q.was_published_recently()
# True


>>> q = Question.objects.get(pk=1)
>>> q.choice_set.all()
# <QuerySet []>


# Create three choices.
>>> q.choice_set.create(choice_text='Not much', votes=0)
# <Choice: Not much>
>>> q.choice_set.create(choice_text='The sky', votes=0)
# <Choice: The sky>
>>> c = q.choice_set.create(choice_text='Just hacking again', votes=0)

# Choice objects have API access to their related Question objects.
>>> c.question
# <Question: What's up?>
>>> q.choice_set.all()
# <QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>
>>> q.choice_set.count()
# 3

# Use double underscores to separate relationships.
# Find all Choices for any question whose pub_date is in this year
>>> Choice.objects.filter(question__pub_date__year=current_year)
# <QuerySet [<Choice: Not much>, <Choice: The sky>, <Choice: Just hacking again>]>

# Let's delete one of the choices. Use delete() for that.
>>> c = q.choice_set.filter(choice_text__startswith='Just hacking')
>>> c.delete()

So basically, we can use python manage.py shell to write some python code and also Django framework syntex.

< Login to Django admin >

- Creating an admin user

python manage.py createsuperuser

Username: admin
Email address: xxxxxx@xxxx
Password: **********
Password (again): *********
Superuser created successfully.

python manage.py runserver

Go to http://127.0.0.1:8000/admin/

And enter username and password.

linooohon@gmail.com

Will see the Django administration

linooohon@gmail.com

- Register our own models in Django admin interface.

  • In the polls/admin.py
from django.contrib import admin

# Register your models here.
from .models import Question, Choice
admin.site.register(Question)
admin.site.register(Choice)

< The End >:

Review:

  • "Project" and "App".
  • Remember Migration Workflow.
  • Using django python shell.
  • Create user for django admin interface and login.

Reference:

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