Create Model in Django - Tutorial for Beginners - 拾光赋-拾光赋

Create Model in Django – Tutorial for Beginners

4年前发布

0406

Hello Coders,

This article aims to help beginners to understand how to Create a Model in Django Framework by coding a new app from scratch and use mostly the terminal. The sample source code can be downloaded from Github (MIT License) and extended for hobby and commercial products. For newcomers, Django is a high-level Python Web framework built by experienced developers that encourages rapid development and clean, pragmatic design.

Thanks for reading! – Content provided by App Generator.

Create Model in Django – source code (Github/MIT License)
More Django Samples provided with authentication, basic modules

Let’s Code Django

Check Python Version – recommended version is Python3


<span>$ </span>python <span>--version</span>
Python 3.8.4        <<span>--</span> All good, we have a 3.x version
<span>$ </span>python <span>--version</span>
Python 3.8.4        <<span>--</span> All good, we have a 3.x version
$ python --version
Python 3.8.4        <-- All good, we have a 3.x version

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Create/activate a virtual environment – Unix-based system


<span>$ </span>virtualenv <span>env</span>
<span>$ </span><span>source env</span>/bin/activate  
<span>$ </span>virtualenv <span>env</span>
<span>$ </span><span>source env</span>/bin/activate  
$ virtualenv env
$ source env/bin/activate

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For Windows, the syntax is slightly different


<span>$ </span>virtualenv <span>env</span>
<span>$ </span>.<span>\e</span>nv<span>\S</span>cripts<span>\a</span>ctivate
<span>$ </span>virtualenv <span>env</span>
<span>$ </span>.<span>\e</span>nv<span>\S</span>cripts<span>\a</span>ctivate
$ virtualenv env
$ .\env\Scripts\activate

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Install Django


<span>$ </span>pip <span>install </span>django
<span>$ </span>pip <span>install </span>django
$ pip install django

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Create a new Django Project


<span>$ </span><span>mkdir </span>django-create-model
<span>$ </span><span>cd </span>django-create-model
<span>$ </span><span>mkdir </span>django-create-model
<span>$ </span><span>cd </span>django-create-model
$ mkdir django-create-model
$ cd django-create-model

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Inside the new directory, we will invoke startproject subcommand:


<span>$ </span>django-admin startproject config <span>.</span>
<span>$ </span>django-admin startproject config <span>.</span>
$ django-admin startproject config .

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Note: Take into account that . at the end of the command.

Setup the database


<span>$ </span>python manage.py makemigrations
<span>$ </span>python manage.py migrate
<span>$ </span>python manage.py makemigrations
<span>$ </span>python manage.py migrate
$ python manage.py makemigrations
$ python manage.py migrate

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Start the app


<span>$ </span>python manage.py runserver 
<span>$</span>
<span>$ </span><span># Access the web app in browser: http://127.0.0.1:8000/</span>
<span>$ </span>python manage.py runserver 
<span>$</span>
<span>$ </span><span># Access the web app in browser: http://127.0.0.1:8000/</span>
$ python manage.py runserver 
$
$ # Access the web app in browser: http://127.0.0.1:8000/

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At this point we should see the default Django page in the browser:

Create a new Django application


<span>$ </span>python manage.py startapp sample
<span>$ </span>python manage.py startapp sample
$ python manage.py startapp sample

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Visualize the default SQL settings – config/settings.py


<span># File: config/settings.py (partial content) </span><span>...</span>
<span>DATABASES</span> <span>=</span> <span>{</span>
    <span>'</span><span>default</span><span>'</span><span>:</span> <span>{</span>
        <span>'</span><span>ENGINE</span><span>'</span><span>:</span> <span>'</span><span>django.db.backends.sqlite3</span><span>'</span><span>,</span>
        <span>'</span><span>NAME</span><span>'</span><span>:</span> <span>BASE_DIR</span> <span>/</span> <span>'</span><span>db.sqlite3</span><span>'</span><span>,</span>
    <span>}</span>
<span>}</span>
<span>...</span>
<span># File: config/settings.py (partial content) </span><span>...</span>
<span>DATABASES</span> <span>=</span> <span>{</span>
    <span>'</span><span>default</span><span>'</span><span>:</span> <span>{</span>
        <span>'</span><span>ENGINE</span><span>'</span><span>:</span> <span>'</span><span>django.db.backends.sqlite3</span><span>'</span><span>,</span>
        <span>'</span><span>NAME</span><span>'</span><span>:</span> <span>BASE_DIR</span> <span>/</span> <span>'</span><span>db.sqlite3</span><span>'</span><span>,</span>
    <span>}</span>
<span>}</span>
<span>...</span>
# File: config/settings.py (partial content) ...
DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.sqlite3',
        'NAME': BASE_DIR / 'db.sqlite3',
    }
}
...

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Define a new model Books in sample application. The below changes should be added to sample/models.py:


<span># File: sample/models.py </span>
<span>from</span> <span>django.db</span> <span>import</span> <span>models</span>                       
<span>class</span> <span>Book</span><span>(</span><span>models</span><span>.</span><span>Model</span><span>):</span>                                 <span># <- NEW </span>    <span>title</span>            <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span>   <span># <- NEW </span>    <span>author</span>           <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span>   <span># <- NEW </span>    <span>publication_date</span> <span>=</span> <span>models</span><span>.</span><span>DateField</span><span>()</span>                 <span># <- NEW </span>
<span># File: sample/models.py </span>
<span>from</span> <span>django.db</span> <span>import</span> <span>models</span>                       

<span>class</span> <span>Book</span><span>(</span><span>models</span><span>.</span><span>Model</span><span>):</span>                                 <span># <- NEW </span>    <span>title</span>            <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span>   <span># <- NEW </span>    <span>author</span>           <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span>   <span># <- NEW </span>    <span>publication_date</span> <span>=</span> <span>models</span><span>.</span><span>DateField</span><span>()</span>                 <span># <- NEW </span>
# File: sample/models.py 
from django.db import models                       

class Book(models.Model):                                 # <- NEW     title            = models.CharField(max_length=100)   # <- NEW     author           = models.CharField(max_length=100)   # <- NEW     publication_date = models.DateField()                 # <- NEW

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Update Project Configuration to use the new model – The sample application must be added in the project configuration to INSTALLED_APPS section.


<span># File: config/settings.py (partial content) </span><span>...</span>
<span>INSTALLED_APPS</span> <span>=</span> <span>[</span>
    <span>'</span><span>django.contrib.admin</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.auth</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.contenttypes</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.sessions</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.messages</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.staticfiles</span><span>'</span><span>,</span>
    <span>'</span><span>sample</span><span>'</span>                        <span># <- NEW </span><span>]</span>
<span>...</span>
<span># File: config/settings.py (partial content) </span><span>...</span>
<span>INSTALLED_APPS</span> <span>=</span> <span>[</span>
    <span>'</span><span>django.contrib.admin</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.auth</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.contenttypes</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.sessions</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.messages</span><span>'</span><span>,</span>
    <span>'</span><span>django.contrib.staticfiles</span><span>'</span><span>,</span>
    <span>'</span><span>sample</span><span>'</span>                        <span># <- NEW </span><span>]</span>
<span>...</span>
# File: config/settings.py (partial content) ...
INSTALLED_APPS = [
    'django.contrib.admin',
    'django.contrib.auth',
    'django.contrib.contenttypes',
    'django.contrib.sessions',
    'django.contrib.messages',
    'django.contrib.staticfiles',
    'sample'                        # <- NEW ]
...

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Tip – for a quick check over latest changes we can run check subcommand.


<span>$ </span>python manage.py check
System check identified no issues <span>(</span>0 silenced<span>)</span><span>.</span>  
<span>$ </span>python manage.py check
System check identified no issues <span>(</span>0 silenced<span>)</span><span>.</span>  
$ python manage.py check
System check identified no issues (0 silenced).

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Generate the SQL code


<span>$ </span>python manage.py makemigrations  <span># generate the SQL code</span>
Migrations <span>for</span> <span>'sample'</span>:
  sample<span>\m</span>igrations<span>\0</span>001_initial.py
    - Create model Book
<span>$ </span>python manage.py makemigrations  <span># generate the SQL code</span>
Migrations <span>for</span> <span>'sample'</span>:
  sample<span>\m</span>igrations<span>\0</span>001_initial.py
    - Create model Book
$ python manage.py makemigrations  # generate the SQL code
Migrations for 'sample':
  sample\migrations\0001_initial.py
    - Create model Book

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Apply changes on database


<span>$ </span>python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sample, sessions
Running migrations:
  Applying sample.0001_initial... OK
<span>$ </span>python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sample, sessions
Running migrations:
  Applying sample.0001_initial... OK
$ python manage.py migrate
Operations to perform:
  Apply all migrations: admin, auth, contenttypes, sample, sessions
Running migrations:
  Applying sample.0001_initial... OK

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Use the model via CLI

Once the model is created we can use it via the Django shell


<span>$ </span>python manage.py shell
<span>>>></span> 
<span>>>></span> from sample.models import Book     <span># import the Book model in our context</span>
<span>>>></span> from django.utils import timezone  <span># used to provide the value for publication_date</span>
<span>>>></span>
<span>>>></span> book1 <span>=</span> Book<span>(</span><span>title</span><span>=</span><span>'The Adventures of Tom Sawyer'</span>, <span>author</span><span>=</span><span>'Mark Twain'</span>, <span>publication_date</span><span>=</span>timezone.now<span>()</span> <span>)</span>
<span>>>></span> book1.save<span>()</span>                       <span># save the new book</span>
<span>$ </span>python manage.py shell
<span>>>></span> 
<span>>>></span> from sample.models import Book     <span># import the Book model in our context</span>
<span>>>></span> from django.utils import timezone  <span># used to provide the value for publication_date</span>
<span>>>></span>
<span>>>></span> book1 <span>=</span> Book<span>(</span><span>title</span><span>=</span><span>'The Adventures of Tom Sawyer'</span>, <span>author</span><span>=</span><span>'Mark Twain'</span>, <span>publication_date</span><span>=</span>timezone.now<span>()</span> <span>)</span>
<span>>>></span> book1.save<span>()</span>                       <span># save the new book</span>
$ python manage.py shell
>>> 
>>> from sample.models import Book     # import the Book model in our context
>>> from django.utils import timezone  # used to provide the value for publication_date
>>>
>>> book1 = Book(title='The Adventures of Tom Sawyer', author='Mark Twain', publication_date=timezone.now() )
>>> book1.save()                       # save the new book

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List all books (using the CLI)


<span>$ </span>python manage.py shell
<span>>>></span> 
<span>>>></span> from sample.models import Book
<span>>>></span> Book.objects.all<span>()</span>
<QuerySet <span>[</span><Book: Book object <span>(</span>1<span>)>]></span>
<span>$ </span>python manage.py shell
<span>>>></span> 
<span>>>></span> from sample.models import Book
<span>>>></span> Book.objects.all<span>()</span>
<QuerySet <span>[</span><Book: Book object <span>(</span>1<span>)>]></span>
$ python manage.py shell
>>> 
>>> from sample.models import Book
>>> Book.objects.all()
<QuerySet [<Book: Book object (1)>]>

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We can see our new book retuned by the query. Let’s improve the information that describe the object.

Django Model – add text representation of an object

To achieve this goal, we should define the __str__() method for the Book model


<span># File: sample/models.py </span>
<span>from</span> <span>django.db</span> <span>import</span> <span>models</span>                       
<span>class</span> <span>Book</span><span>(</span><span>models</span><span>.</span><span>Model</span><span>):</span> 
    <span>title</span>            <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span> 
    <span>author</span>           <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span>
    <span>publication_date</span> <span>=</span> <span>models</span><span>.</span><span>DateField</span><span>()</span> 
    <span>def</span> <span>__str__</span><span>(</span><span>self</span><span>):</span>       <span># <- NEW </span>        <span>return</span> <span>self</span><span>.</span><span>title</span>    <span># <- NEW </span>
<span># File: sample/models.py </span>
<span>from</span> <span>django.db</span> <span>import</span> <span>models</span>                       

<span>class</span> <span>Book</span><span>(</span><span>models</span><span>.</span><span>Model</span><span>):</span> 
    <span>title</span>            <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span> 
    <span>author</span>           <span>=</span> <span>models</span><span>.</span><span>CharField</span><span>(</span><span>max_length</span><span>=</span><span>100</span><span>)</span>
    <span>publication_date</span> <span>=</span> <span>models</span><span>.</span><span>DateField</span><span>()</span> 

    <span>def</span> <span>__str__</span><span>(</span><span>self</span><span>):</span>       <span># <- NEW </span>        <span>return</span> <span>self</span><span>.</span><span>title</span>    <span># <- NEW </span>
# File: sample/models.py 
from django.db import models                       

class Book(models.Model): 
    title            = models.CharField(max_length=100) 
    author           = models.CharField(max_length=100)
    publication_date = models.DateField() 

    def __str__(self):       # <- NEW         return self.title    # <- NEW

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Let’s restart the Django console and check the results:


<span>$</span> <span>python</span> <span>manage</span><span>.</span><span>py</span> <span>shell</span>
<span>>>></span> 
<span>>>></span> <span>from</span> <span>sample.models</span> <span>import</span> <span>Book</span>
<span>>>></span> <span>Book</span><span>.</span><span>objects</span><span>.</span><span>all</span><span>()</span>
<span><</span><span>QuerySet</span> <span>[</span><span><</span><span>Book</span><span>:</span> <span>The</span> <span>Adventures</span> <span>of</span> <span>Tom</span> <span>Sawyer</span><span>></span><span>]</span><span>></span>
<span>$</span> <span>python</span> <span>manage</span><span>.</span><span>py</span> <span>shell</span>
<span>>>></span> 
<span>>>></span> <span>from</span> <span>sample.models</span> <span>import</span> <span>Book</span>
<span>>>></span> <span>Book</span><span>.</span><span>objects</span><span>.</span><span>all</span><span>()</span>
<span><</span><span>QuerySet</span> <span>[</span><span><</span><span>Book</span><span>:</span> <span>The</span> <span>Adventures</span> <span>of</span> <span>Tom</span> <span>Sawyer</span><span>></span><span>]</span><span>></span>
$ python manage.py shell
>>> 
>>> from sample.models import Book
>>> Book.objects.all()
<QuerySet [<Book: The Adventures of Tom Sawyer>]>

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Use the model via Admin Section

Django comes with an admin section our-of-the box that allows us to manage with ease all models defined in project.
To manage the Book model in the administration console we need to create a superuser (aka the admin) and after register the Book model to be visible in the admin section.

Create the superuser


<span>$ </span>python manage.py createsuperuser
sername <span>(</span>leave blank to use <span>'sm0ke'</span><span>)</span>: admin
Email address: admin@appseed.us
Password: 
Password <span>(</span>again<span>)</span>:
Superuser created successfully.
<span>$ </span>python manage.py createsuperuser
sername <span>(</span>leave blank to use <span>'sm0ke'</span><span>)</span>: admin
Email address: admin@appseed.us
Password: 
Password <span>(</span>again<span>)</span>:
Superuser created successfully.
$ python manage.py createsuperuser
sername (leave blank to use 'sm0ke'): admin
Email address: admin@appseed.us
Password: 
Password (again):
Superuser created successfully.

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Register Book model to be visible in the admin section – Edit sample/admin.py as below:


<span># File: sample/admin.py </span>
<span>from</span> <span>django.contrib</span> <span>import</span> <span>admin</span>
<span>from</span> <span>.models</span> <span>import</span> <span>Book</span>        <span># <- NEW </span>
<span>admin</span><span>.</span><span>site</span><span>.</span><span>register</span><span>(</span><span>Book</span><span>)</span>       <span># <- NEW </span>
<span># File: sample/admin.py </span>
<span>from</span> <span>django.contrib</span> <span>import</span> <span>admin</span>

<span>from</span> <span>.models</span> <span>import</span> <span>Book</span>        <span># <- NEW </span>
<span>admin</span><span>.</span><span>site</span><span>.</span><span>register</span><span>(</span><span>Book</span><span>)</span>       <span># <- NEW </span>
# File: sample/admin.py 
from django.contrib import admin

from .models import Book        # <- NEW 
admin.site.register(Book)       # <- NEW

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Authenticate as admin – http://localhost:8000/admin/

At this point we should see the Books model in the UI and able to execute CRUD operations.

Create Django Model – List Model Items

Django Create Model – Edit Records

Thanks for reading! Feel free to AMA in the comments section.

More Django Resources

Read more about Django (official docs)
Start fast a new project using development-ready Django Starters

原文链接：Create Model in Django – Tutorial for Beginners

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