reference

Django REST API

| Udemy]]

KickStart

manage.py command line

runserver

makemigrations

1. create a new migration plan

migrate

createsuperuser

startapp

1. create a new app/rest API

shell

help

/admin URL for admin user

A django APP

An app in a Django project is a Python package that does a particular job. A Django project contains one or more apps and each of them handles a particular task. For example, a Django blog website will have a list of posts, user authentication, user profiles, etc. The best practice is to create different apps for each one of them.

Apps are meant to be portable and can be shared between different projects. For example, a Django e-commerce website and a Django blog website both will have user authentication. You can make a single app for user authentication and share it between different Django projects.

create a new APP

python manage.py startapp [app name]

Project structure

project structure

`manage.py~ file provides a command-line utility for a Django project.

*** _asgi stands for Asynchronous Server Gateway Interface and ~wsgi` stands for *Web Server Gateway Interface.*

1. After your development process is completed, you will move to production and hosting. For hosting you will use ~asgi~ or ~wsgi~ compatible servers. According to the type of server you use, you have to import middleware accordingly.

2. ~asgi.py~ enables ASGI compatible servers and ~wsgi.py~ enables WSGI compatible servers to serve your Django web app.

settings.py

1. This is the main configuration file for a Django project. This is the main settings file and here you will configure all the apps and middleware for your project.

2. This file also handles the database settings. By default Django uses sqlite3. But if you use a different database, which you will most probably do, you will configure it in ~settings.py~.

3. ~settings.py~ also handles templates, static files, and media files related settings.

urls.py

1. URLs are different endpoints of your website. ~urls.py~ contains the URL configurations for your website. By default, ~urls.py~ comes with the URL pattern for the admin panel. You will create other endpoints for your web app in this file.

Inside your APP

1. admin.py

   1. This file is used to register the models in your app in the Django administration. You will use this file to display the models of your app in the admin panel.

   2. e.g. register article

      from django.contrib import admin
      from .models import Article
      
      # Register article models here.
      admin.site.register(Article)
      

2. app.py

   1. It is a common configuration file for all Django apps. You can configure the attributes for your app using this file. However, the default configuration is sufficient for most cases. So, adding app configuration is a rare case.

3. ~migrations~ folder

   1. Once you start making changes in your database, the ~migrations~ folder will be populated with the records for all those migrations.

4. models.py

5. You create your models in this file. Models define the database structure of your app. In ~models.py~ you basically create database tables for your app with proper relationships using Python classes.

6. ~models.py~ is one of the most important files in your app. Django follows the MVT (Model-View-Template) design architecture. The 'M' represents models. So, models are one of the basic components of a Django app.

7. views.py

   1. is another important file. Views are the 'V' of MVT. Views provide an interface through which users interact with a Django website. It connects models and templates together.

   2. In this file, you write the business logic for your app. A view can be either function-based or class-based. You decide if you want to write your views using functions or classes.

   3. You can learn more about the MVT architecture from this article:

   4. The MVT Design Pattern of Django

8. tests.py

   1. is where you write test codes for your app. It is used to test the overall working of a Django app.

Other folder/files

1. Templates

   1. django MVT *T*emplate

   2. each app can have own template and the search sequence is defined same as how different app is loaded

2. static

   1. css, js, images, json..

   2. {% raw %}{% load static %}{% endraw %} to load static files 👍

   3. {% raw %}{% static 'css/bootstrap.css' %}{% endraw %} to refer to those files

3. urls.py in app

   1. if your application is complex, use a dedicatd url.py

4. forms.py

   1. If your website expects to receive user inputs you need to use forms. To work with forms in an app you need to create the forms.py file in that app. Here you will write the codes to handle forms.

Request and response Request & Response 4.2

Requests

1. method, GET, POST (used for form submit)， META

2. Query parameters /query/?id=123 #card

   1. request.Get.get('id')

      <form>
      <input type="text" name="id" value = "{{search_data}}">
      <button type="submit">search</button>
      </form>
      

Reponse

1. HttpResponse; render; redirect

Models

Default and AutoField

BigAutoField(64bit) and AutoField

app.py set default auto field

default_auto_field = "django.db.models.BigAutoField"

1. if default_autofield present, each table will have id and you do not need to define aut-inc auto field

ForeignKey and auto join

define a foreigh key relationship #card

depart = models.ForeignKey(
  "Department",
  on_delete=models.CASCADE
xx)
# table "Department", to_field='id'
# if 'id' is default (auto_field) to_field can be ignore

card

1. django will append id and create depart_id automatically from depart for foreign key #magic

2. on_delete should be specified. Normally CASCADE, can also be SET_NULL if it is nullable

AutoJoin

1. Instead of join two table to get info from 2^nd table like this

   user = model.User.objects.filter(id=1).first()
   user_depart = models.Department.objects.filter(id=user.depart_id).first()
   

   Django know how two table are associated and We can dereference department info with depart field directly without filter(id=user.depart_id)

   print(user.depart.id)
   print(user.depart.name)
   

enum with choices

define with {field_name}_choices

gender_choices = ( (1,"Male"),(2,"Female") )
gender = models.SmallIntegerField(choices=gender_choices,default=1)

when retrieve gender value, it will be ½. But it can be display nicely with #magic method models.get_{field_name}_display() e.g. get_gender_display() will show Male|Female

order_by()

order_by("field_name")

reverse order with order_by("-field_name")

* *

filter() with magic naming

filter with field and value (field name : myid in all examples )

Number filter

1. filter(myid__gt=12) -> value >12, You can also filter on myid__lte myid_lt etc

String filter

1. mytext__startwith, mytext__endwith, mytext__contains

Multi field filter : filter(myid_gte=12, mytext_contains="123")

pagination

*

Django Template

Abstract

A template is a text file. It can generate any text-based format (HTML, XML, CSV, etc.).

A template contains *variables*, which get replaced with values when the template is evaluated, and *tags*, which control the logic of the template.

-----

:main-idea-checkbox:

• What is this aims?
• What is the their research question?
• What is the author arguing?
• What is their answer to the question?
• What points support their argument?
• What are their main reasons?
• What evidence have they used to support their argument?
• What’s the significance of these facts?
• What principle are they based on?
• How can I apply them?  How do they fit in with what I already know?
• What’s beyond them?
• What're supporting details and explanations?

::: {.END .drawer} :::

Cheatsheet

render(request, 'template_file.html', {"var1": value, "var2", value})

{{ var1 }}
{{ listVar.1 }} <!-- listVar[0] -->
{% raw %}{% for item in lst %}{% endraw %}  <!-- loop list -->
<span> {{ item }} </span>
{% raw %}{% endfor %}{% endraw %}

<span> {{ dict }} </span> <!-- object  -->
<span> {{ dict.name }} </span> <!-- object attribute -->

{{ list.1.name }}  <!-- list[1].name

Loop and condition

{% raw %}{% for item in dict.keys %}{% endraw %}  <!-- loop object  -->
<span> {{ item }} </span>
{% raw %}{% endfor %}{% endraw %}

{% raw %}{% for k, v in dict.items %}{% endraw %}  <!-- loop object  -->
<span> {{ k }} = {{ v }} </span>
{% raw %}{% endfor %}{% endraw %}

{% raw %}{% if n == 'xxx' %}{% endraw %}
<h1> xxxx </h1>
{% raw %}{% elif n == "XXX" %}{% endraw %}
<h1> XXX </h1>
{% raw %}{% else %}{% endraw %}
<h1> ssss </h1>
{% raw %}{% endif %}{% endraw %}

Template tags {% raw %}{% ... %}{% endraw %} generally do not require double curly braces or quotes for variable names, as they inherently expect Python-like syntax.

value="{{ title|default:'depart name' }}" or value={{ title|default:'depart name' }}

1. double quotes is strongly recommended

Call a function inside {{}} or {% raw %}{% %}{% endraw %}

1. {{ obj.get_gender_display() }} is invalid. You can not call a function with () inside {{}}, use {{ obj.get_gender_display }} instead

2. How about arguments? see ((651c1c60-a6bd-47c4-9b9a-889f3d41cf5f))

Template extends

extends tag is used for inheritance of templates in django. One needs to repeat the same code again and again. Using extends we can inherit templates as well as variables.

syntax

{% raw %}{% extends 'template_name.html' %}{% endraw %}

# examples
{% raw %}{% extends "./base2.html" %}{% endraw %}
{% raw %}{% extends "../base1.html" %}{% endraw %}
{% raw %}{% extends "./my/base3.html" %}{% endraw %}

extends examples

1. template.html

   <h1>Main Template</h1>
   {% raw %}{% block content %}{% endraw %}
   {% raw %}{% endblock %}{% endraw %}
   

2. extends.html overwrite block: content

   {% raw %}{% extends "template.html" %}{% endraw %}
   
   {% raw %}{% block content %}{% endraw %}
   <h2> GeeksForGeeks is the Best
   {% raw %}{% endblock %}{% endraw %}
   

3. block can extends anything, e.g css reference, js code blocks etc

pipe operator | and filter

In Django template language, the pipe character | is used to apply filters to variables. Filters are used to format variables or perform some operation on them before they are rendered in the template.

Syntax

{{ variable|filter_name:"argument" }}
Sample:
{{ my_list|join:", "|escape }}

1. |join:", ": The join filter concatenates items in the list into a single string, using ~, ~(comma and space) as a separator.

As function call with parameter is not allowed inside template, do this instead

<td class="py-2 px-4">{{ obj.create_time.strftime('%Y-%m-%d') }}</td>
Should be write as
<td class="py-2 px-4">{{ obj.create_time | date:'Y-m-d' }}</td>

include another template file

top.html

<div class = '{{ mycss }}'> this is header </div>

index.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>

{% raw %}{% include 'top.html' with mycss="acss" %}{% endraw %}

<h2> 网页body部分 </h2>

</body>
</html>

include passing multiple values

{% raw %}{% include "name_snippet.html" with person="Jane" greeting="Hello" %}{% endraw %}

And with django variables from python codes

{% raw %}{% extends 'base.html' %}{% endraw %}

{% raw %}{% block panel %}{% endraw %}
{% raw %}{% include 'form.html' with title=title id=id %}{% endraw %}
{% raw %}{% endblock %}{% endraw %}

Form

Django’s form functionality can simplify and automate vast portions of this work, and can also do it more securely than most programmers would be able to do in code they wrote themselves.

Django handles three distinct parts of the work involved in forms:

preparing and restructuring data to make it ready for rendering

creating HTML forms for the data

receiving and processing submitted forms and data from the client

flowChart-1

Create a form

How to create a FormClass #card

1. Sample

   from django import forms
   
   class FormName(forms.Form):
            # each field would be mapped as an input field in HTML
           field_name = forms.Field(**options)
   

   card #card

Form class sample

from django import forms

class InputForm(forms.Form):
    first_name = forms.CharField(max_length = 200)
    last_name = forms.CharField(max_length = 200)
    roll_number = forms.IntegerField(
                    help_text = "Enter 6 digit roll number"
                    )
    password = forms.CharField(widget = forms.PasswordInput())

1. Note if field defined as auto (auto_now, auto_now_add), it may not shown in Form

Form view.py

from django.shortcuts import render
from .forms import InputForm
def home_view(request):
    context ={}
    context['form']= InputForm()
    return render(request, "home.html", context)

Render in template

1. A form comes with 3 in-built methods that can be used to render Django form fields.

2. {{ form.as_table }} will render them as table cells wrapped in \<tr> tags

3. {{ form.as_p }} will render them wrapped in \<p> tags

4. {{ form.as_ul }} will render them wrapped in \<li> tags

Template:

There are a few ways to present form objects

• Field by field

<form action = "" method = "post">
    {{ form.first_name }}
    {{ form.last_name }}
    {{ form.phone_number }}
    <input type="submit" value=Submit">
</form>

• Loop

<form action = "" method = "post">
    {% raw %}{% csrf_token %}{% endraw %}
    {% raw %}{% for field in form %}{% endraw %}
    {{ field }}
    {% raw %}{% endfor %}{% endraw %}
    <input type="submit" value=Submit">
</form>

• {{ form }}

<form action = "" method = "post">
    {% raw %}{% csrf_token %}{% endraw %}
    {{ form }}
    <input type="submit" value=Submit">
</form>

Validate a form object

The easiest way to validate a single field is to override the method clean_<fieldname>() for the field you want to check. e.g. Validate renewal_date field

import datetime
from django import forms
from django.core.exceptions import ValidationError
from django.utils.translation import gettext_lazy as _
class RenewBookForm(forms.Form):
    renewal_date = forms.DateField(help_text="Enter a date between now and 4 weeks (default 3).")

    def clean_renewal_date(self):
        data = self.cleaned_data['renewal_date']
        # Check if a date is not in the past.
        if data < datetime.date.today():
            raise ValidationError(_('Invalid date - renewal in past'))

        # Check if a date is in the allowed range (+4 weeks from today).
        if data > datetime.date.today() + datetime.timedelta(weeks=4):
            raise ValidationError(_('Invalid date - renewal more than 4 weeks ahead'))

        # Remember to always return the cleaned data.
        return data

Django Form from Models

If the form is coupled with database table, it is easy to use ModelForm

Models

1. Sample:

   from django.db import models
   class Movie(models.Model):
       movie_title = models.CharField(max_length=150)
       release_year = models.IntegerField()
       director = models.CharField(max_length=100)
       movie_poster = models.ImageField(upload_to='images/', None=True)
       movie_plot = models.TextField()
       def __str__(self):
           return self.movie_title  # when print movie object it shows title. Also useful
           #when movie object is showed in dropdown etc
   

2. FieldValidator

   1. django.core.validators

      mobile = forms.CharField(label = "mobile number"
          validators=[RegexValidator(r'^159[0-9]+$', 'mobile start with 159') ],
      )
      

3. A disabled field

   1. For read only field set disabled=True, e.g. mobile = forms.CharField(disabled=True, label='mobile number')

Create ModelForm class

1. How to create a ModelForm Class #card

   1. Code

      from django import forms
      from .models import Movie
      
      class MovieForm(forms.ModelForm):
          class Meta:
              model = Movie
              fields = ('movie_title', 'release_year', 'director', 'movie_poster', 'movie_plot')
      

2. Sample

   from django import forms
   from .models import Movie
   
   
   # Create your forms here.
   class MovieForm(forms.ModelForm):
   
       class Meta:
           model = Movie
           fields = ('movie_title', 'release_year', 'director', 'movie_poster', 'movie_plot')
   

3. The Meta class is used to change the behavior of the ModelForm . Within it, specify the model your fields come from and the fields you want to use from that model.

4. Key components of Meta class in ModelForm #card

   1. model the data model class

   2. fields: the fields will be shown in the form

   3. widgets: used to generate HTML code that override default behavior. e.g. inputbox with CSS styling

5. Explains of Meta class

   • model The Model class
   • fields It is strongly recommended that you explicitly set all fields that should be edited in the form using the fields attribute. Failure to do so can easily lead to security problems when a form unexpectedly allows a user to set certain fields, especially when new fields are added to a model. If those are not your concerns ~fields = "[[all]{.underline}]{.underline}" ~ can easy your job
   • exclude Set the exclude attribute of the ModelForm’s inner Meta class to a list of fields to be excluded from the form.

   class PartialAuthorForm(ModelForm):
       class Meta:
           model = Author
           exclude = ['title']
   

   • field_classes or formfield_callback can be used to customize the type of fields instantiated by the form.
   • widgets: override default forms.TextInput, It is helpful if you need setup css e.g.

   class PartialAuthorForm(ModelForm):
       class Meta:
           model = Author
           exclude = ['title']
           widgets = {
               "name": forms.widgets.TextInput(attrs={"class": "form-control"}),
               "password": forms.widgets.PasswordInput(attrs={"class": "form-control"}),
               "age": forms.widgets.NumberInput(attrs={"class": "form-control"}),
               "account": forms.widgets.NumberInput(attrs={"class": "form-control"}),
               "department": forms.widgets.Select(attrs={"class": "form-control"}),
           }
   

   • If you want to apply same attributes for all field, do this instead by override __init__

   class UserModelForm(forms.ModelForm):
       def __init__(self, *args, **kwargs):
           super().__init__(*args, **kwargs)
           for name, field in self.fields.items():
               field.widget.attrs["class"] = style
               if name == "password":
                   field.required = False  # Make the password field optional
                   field.widget = forms.widgets.PasswordInput(attrs={"class": style})
       class Meta:
           model = UserInfo
           fields = "__all__" # It can be a list of all fields you want to display
        # password field can also be setup here
        # password = forms.CharField(required=False, widget=forms.PasswordInput()) # some field need special attention
        # can also  be put here
   

   • Error messages

   You can reuse the default error messages. In case the message need to be customered for specific field

   error_messages = {
         "name": {
             "required": "用户名不能为空, 并且不能重复",
         },
         "age": {
             "required": "年龄不能为空， 并且应该处于0~140",
         },
     }
   

6. Add New field to ModelForm

   1. e.g. Add password confirm input field

      class UserModelForm(forms.ModelForm):
        confirm_password = forms.CharField(
              label = "please input password again",
              widget = forms.PasswordInput(render_value=True)
          )
          def __init__(self, *args, **kwargs):
              super().__init__(*args, **kwargs)
              for name, field in self.fields.items():
                  field.widget.attrs["class"] = style
                  if name == "password":
                      field.required = False  # Make the password field optional
                      field.widget = forms.widgets.PasswordInput(attrs={"class": style})
          class Meta:
              model = UserInfo
              fields = "__all__"
      

   2. render_values allow pre-fill values

The html template

<form method="post" enctype="multipart/form-data">
  {% raw %}{% csrf_token %}{% endraw %}
      {{movie_form}}
      <button class="btn btn-primary my-4" type="submit">Submit</button>
</form>

For ((651b71c9-7e23-4638-a89c-240b474388a8)) Add __str__

class Department(models.Model):
    title = models.CharField(verbose_name="Department", max_length=32)
    def __str__(self):
        return self.title

So that when adding user's department in the dropdown, it will show the title instead of "Python Object"

Create a ModelForm object #card

1. an empyt object (create a new entry) form = UserModelForm()

2. From a POST request (for parse form submit and save data) form = userModelForm(request.POST)

3. From database instance (foir re-edit data) form = UserModelForm(instance=models.User.objects.filter(id=id).first())

4. From both POST and database (normally when reedit data when form submission failed) form = UserModelForm(request.POST, instance=models.User.objects.filter(id=id).first())

Save ModelForm(),

1. You can either parse the POST request and get all fields, You can Also do:

   form = UserModelForm(request.POST)  # POST to form class
   if form.is_valid():
       form.save()  # save to DB
       return redirect("/user/list/")
   # invalid data auto refill the form and you can re-send again
   return render(request, "user_add.html", {"form": form})
   

Handle form errors

**

Pagination

with python slicing [start:end]

qs = models.Users.objects.all()
qs = models.Users.objects.filter(id=123)[0:10]
qs = models.Users.objects.filter(id=123)[10:20]

qs = models.Users.objects.filter(id=123).order_by('name')[0:20]
qs = models.Users.objects.filter(id=123).order_by('name')[20:40]

page = int(request.GET.get('page', 1))
qs = models.Users.objects.filter(id=123).order_by('name')[(page-1)*page_size:page*page_size]

django template

<ul class='pagination'>
  <li><a href="?page=1">1</a></li>
  <li><a href="?page=2">2</a></li>
</ul>

Pagination generate by python

from django.utils.safestring import mark_safe
...
total = models.Users.objects.filter(id=123).order_by('name').count()
total_pages = totla//page_size + 1
start = cur_page - 5
end = cur_page + 5
for i in range(start, end + 1):
  sel = '""'
  if i == page:
    sel = f'"active"'
  ele = f'<li class={sel} ><a href="?page={i}">{i}</a></li>'
  page_list.append(ele)
page_string=mark_safe(''.join(page_list))
return render(request, 'list.html', {"queryset": qs, "page_list": page_string})

Template

<ul class="pagination">
    <li><a href="{{ head_page }}" aria-label="Previous"><span aria-hidden="true">首页</span></a></li>
    {{ page_string }}
    <li><a href="{{ end_page }}" aria-label="Next"><span aria-hidden="true">尾页</span></a></li>

</ul>
<br>

<form method="get">
    <div style="display:inline-block; width: 150px;">
        <div class="input-group">
            <span> <input type="text" class="form-control" placeholder="请输入页码" name="page"></span>
            <span class="input-group-btn">
                <button class="btn btn-primary" type="submit">跳转</button>
            </span>
        </div>
    </div>
</form>

FBV and CBV

FBV: Function based View

sample

def my_create_view(request, pk):
  template_name = 'form.html'
  form_class = MyForm

  form = form_class

  if request.method == 'POST':
    form = form_class(request.POST)
    if form.is_valid():
      form.save()
      return HttpResponseRedirect(reverse('list-view'))
  elif request.method == 'PUT':
    return ...
  return render(request, template_name, {'form': form})
# url

CBV: Class based view

use as_view() and internally use dispatch()

Pros

1. reuseablity by inherited another view

2. DRY

3. extendability

Cons

1. Implicit code flow

2. decorators require extra override

sample

class MyCreateView(View):
  template_name = 'form.html'
  form_class = MyForm

  def get(self, request, *args, **kwargs):
    form = self.form_class
    return render(request, template_name, {'form': form})

  def post(self, request, *args, **kwargs):
    form = self.form_class(request.POST)
    if form.is_valid():
      form.save()
      return HttpResonseRedirect(reverse('list-view'))
    else:
      return render(request, self.template_name, {'form': form})
# URL
urlpatterns = [
    url(r'^new/$', MyCreateView.as_view(), name='original-create-view')
    url(r'^new_two/$', MyCreateView.as_view(template_name='other_form.html', form_class='MyOtherForm'), name='modified-create-view')
  ]

Django’s views requirements:

callable. CBV has as_view()

accept HttpRequest as first positional argument

return HttpResponse or raise exception

reference: Django : Class Based Views vs Function Based Views | by Sarthak Kumar | Medium

which should you use

what type of view should use

If it is single method (e.g. Get only) use FBV otherwise CBV