Python-Django/C2/Creating-Django-Models/English - Revision history

Nancyvarkey at 00:35, 8 November 2019

2019-11-08T00:35:40Z

Nancyvarkey at 10:40, 11 September 2018

2018-09-11T10:40:43Z

Pravin1389: Created page with "'''Title of script:''' Creating Django Models '''Keywords:''' Video tutorial, Django app, Django Model, Python Django, Django database migration {| border=1 |- || Visual cue..."

2018-09-05T12:33:21Z

Created page with "'''Title of script:''' Creating Django Models '''Keywords:''' Video tutorial, Django app, Django Model, Python Django, Django database migration {| border=1 |- || Visual cue..."

New page

'''Title of script:''' Creating Django Models

'''Keywords:''' Video tutorial, Django app, Django Model, Python Django, Django database migration

{| border=1
|-
|| Visual cue
|| Narration
|-
|| Slide: Creating Django Models
|| Hello and welcome to the spoken tutorial on “'''Creating Django Models'''”.
|-
|| Slide: Learning Objectives
|| In this tutorial, we will learn to:

* Create a '''blog app'''
* Initialize a '''Django app'''
* Create a '''Django model '''and
* Perform '''Database''' migration

|-
|| Slide: System Requirements
|| To record this tutorial, I am using

* '''Ubuntu Linux 16.04 OS '''
* '''Python 3.5 '''
* '''Python 3.4-venv''' or higher and
* '''gedit Text Editor'''

|-
|| Slide: Prerequisites
|| To follow this tutorial, you need to know

* How to create a '''Django project'''
* If not, then please go through the pre-requisite tutorials in this series.

|-
|| Slide: Django App
|| * A '''Django project''' typically contains one or more '''apps'''
* A '''Django app''' performs a particular task
* A '''Django app''' will have one or more '''models'''

|-
|| Slide: What is a Django Model?
|| A '''Django model''' is a simple '''Python class.'''
* A '''Model class '''represents a '''database table '''
* A '''Model attribute '''represents a '''table field '''(each column in the '''table''')
* We write '''Django models '''in the '''models.py''' file

|-
|| Slide: Creating Django Models for blog app
|| In this tutorial, we will learn to create two models''' 'Blog' '''and ''''Article'''' in the '''blog app.'''

The ''''Blog' model '''will have 2 '''fields''':
* '''name '''and
* '''created_on'''

|-
|| Slide: Creating Django Models for blog app
|| The ''''Article' model''' will have 5 '''fields''':
* '''blog'''
* '''created_on'''
* '''title'''
* '''body '''and
* '''draft'''

|-
|| Open a Terminal window
|| Let us open the '''terminal''' by pressing '''Ctrl''', '''Alt''' and '''T''' keys simultaneously on the keyboard.
|-
|| [Terminal]

Type cd my-django & Press Enter
|| Using the '''cd''' '''command, '''go to the folder '''my hyphen django''' which we had created earlier.
|-
|| [Terminal]

Type source myapp_env/bin/activate and press Enter
|| Let us activate the '''virtual environment myapp underscore env.'''

To do so type '''source <space> myapp underscore env slash bin slash activate '''

And press '''Enter'''.
|-
|| [Terminal]

cd mysite & Press Enter
|| Now let us go to the '''mysite''' folder by typing

'''cd <space> mysite''' and press '''Enter'''.
|-
||
|| Here onwards, please remember to press the '''Enter''' key after typing each '''command'''.
|-
|| [Terminal]

Type python manage.py startapp blog and press Enter
|| For this demo, let us create a '''blogging app''' named ''''blog''''.*

So type '''python <space> manage dot py <space> startapp <space> blog'''
|-
|| Switch to Slide
|| We have successfully created the '''blog app.'''

Let us now see the '''app''' file structure.
|-
|| Slide:File structure

blog/

_init_.py

admin.py

apps.py

migrations/

_init_.py

models.py

tests.py

views.py
|| startproject command creates a project consisting of a file structure as shown here

|-
|| [Terminal]
|| Switch back to '''terminal.'''
|-
|| [Terminal]

Type ls and press enter
|| Let us see the '''blog app directory '''in our '''project'''.

Type '''ls'''
|-
|| [Terminal]

Highlight blog
|| We can see a '''directory '''named '''blog'''.
|-
|| [Terminal]

Type ls blog and press Enter
|| Now, type '''ls <space> blog''' to list the files in the '''blog app.'''
|-
|| [Terminal]

Point to the blog file structure in the terminal
|| We see the file structure of the '''blog app.'''

We will understand this structure in detail later in this series.
|-
|| [Terminal]

Highlight

blog app
|| Now our '''project ‘mysite’''' has to detect the '''blog app'''.

So, we should add the '''app''' name into '''settings.py''' file, which is present in the '''mysite directory.'''
|-
|| [Terminal]

Type gedit mysite/settings.py & and press Enter
|| Let us open the '''settings.py''' file in any text editor.

I will be using '''gedit''' text editor.

Type''' gedit <space> mysite slash settings dot py <space> ampersand'''
|-
|| [settings.py]

Point to INSTALLED_APPS
|| Locate the line '''INSTALLED_APPS.'''

Let us add the '''app config '''line at the beginning of the '''INSTALLED_APPS''' value.
|-
|| [settings.py]

Type ‘blog.apps.BlogConfig’,
|| Type '''within single quotes blog dot apps dot BlogConfig comma'''

Now, the '''blog app''' will be detected by our '''project'''.

With this we have '''initialized '''the '''blog app.'''
|-
|| Press Ctrl+S
|| Press '''Ctrl''' and '''S''' keys to save the changes and close the file.
|-
|| [Terminal]

Type gedit blog/models.py & and press Enter
|| Now, let us build '''models''' in this '''blog app.'''

Type '''gedit <space> blog slash models dot py <space> ampersand'''
|-
|| [models.py]

Highlight
from django.db import models

<nowiki># Create your models here.</nowiki>
|| We are now in the '''models.py''' file.

Each '''model''' is a '''Python class''' that inherits from the '''django db models Model.'''

First let us add a '''model''' named''' Blog.'''
|-
|| [models.py] Type:

class Blog(models.Model):

name = models.CharField(max_length=120)

created_on = models.DateTimeField(auto_now_add=True)
|| To add the '''model''' '''class''' with the '''database''' '''fields, '''type the code as shown here.
|-
|| [models.py]

Highlight class
|| Here '''class''' is a special '''keyword''' that indicates that we are defining an object.
|-
|| [models.py]

Highlight Blog
|| '''Blog''' is the name of our '''model.'''

We can give it any name, but we must avoid special characters and whitespaces.
|-
|| [models.py]

Highlight (models.Model)
|| Our '''Blog model''' is inherited from the '''django db models Model.'''
|-
|| [models.py]

Highlight name
|| Every '''attribute '''of the '''class''' is a '''field''' of the '''table.'''

A '''Field''' is used to describe the mapping of the '''model attributes''' to the '''database columns.'''
|-
|| [models.py]

Highlight models.CharField
|| '''CharField''' defines the text with a limited number of characters.

|-
|| [models.py]

Highlight
(max_length=120)
|| The '''max underscore length''' is enforced at the '''database level''' and in '''Django’s validation.'''

Here, the character length is one hundred and twenty.
|-
|| [models.py]

Highlight models.DateTimeField
|| '''Django’s DateTimeField''' is a very useful '''argument''' for automatically managing the date and time.

|-
|| [models.py]

Highlight (auto_now_add=True)
|| The '''auto_now_add''' will set the very first creation time of the object.
|-
|| [models.py] Type:

class Article(models.Model):

blog = models.ForeignKey(Blog, on_delete=models.CASCADE)

created_on = models.DateTimeField(auto_now_add=True)

title = models.CharField(max_length=120)

body = models.TextField()

draft = models.BooleanField(default=False)
|| Now, let us add the other '''model Article.'''

Type the code as shown here.
|-
|| [models.py]

Highlight models.ForeignKey
|| Here '''models.ForeignKey''' is a link to another '''model.'''

This will create an '''object''' that has a many-to-one relationship.
|-
|| [models.py]

Highlight (Blog, on_delete=models.CASCADE)
|| A many-to-one relationship requires two positional '''arguments.'''

The '''class''' to which the '''model''' is related and the '''on_delete''' option.
|-
|| [models.py]

Highlight

on_delete=models.CASCADE
|| '''on_delete argument''' is required when adding a '''ForeignKey field.'''

In''' SQL '''there is constraint named '''ON DELETE CASCADE.'''

Here '''Django '''reproduces the same behaviour.
|-
|| [models.py]

Highlight

CASCADE
|| When the referenced '''object''' is deleted, it also deletes the '''objects''' that have references to it.
|-
|| [models.py]

Highlight

models.DateTimeField(auto_now_add=True)
|| Similar to the '''Blog Model''', '''created_on''' creates the '''DateTimeField''' for the '''Article''' '''model'''.
|-
|| [models.py]

Highlight

models.CharField
|| Next, we are inserting the '''Article’s''' title which is a '''character type Field.'''

|-
|| [models.py]

Highlight

models.TextField()
|| This is to accommodate a long text that does not require a text limit to be specified.
|-
|| [models.py]

Highlight

models.BooleanField(default=False)
|| The next '''field '''contains either '''True''' or '''False.'''

Here we have set the default value as '''False.'''
|-
|| Save the code Ctrl + S

|| This is how we have added our '''Models Blog '''and '''Article'''.

Now, save and close the file.

Clear the '''terminal'''
|-
|| [Terminal]

Type python manage.py --help
|| The next step is the migration of our '''Model '''to the '''database'''.

For '''help''', type

'''python manage dot py <space> hyphen hyphen help'''
|-
|| [Terminal]

Point to the shell prompt
|| Here, we can see the list of available commands and options.
|-
|| [Terminal]

Highlight

makemigrations
|| '''makemigrations''' will create new migrations based on the changes in your '''model'''.
|-
|| [Terminal]

Highlight

migrate
|| '''migrate''' applies the changes noted during the '''makemigrations''' phase.
|-
|| [Terminal]

Type python manage.py migrate and press Enter
|| Now, type

'''python <space> manage dot py <space> migrate'''
|-
|| [Terminal]

(Running migrations)

|| The '''migrate command''' looks at the '''INSTALLED_APPS''' setting.

It will create a '''database''' for all the existing '''apps '''in the '''settings dot py '''file.
|-
|| [Terminal]

Highlight

Apply all migrations:

admin, auth, contenttypes, session
|| The '''migrate command''' will only run migrations for the '''apps '''in '''INSTALLED_APPS.'''

|-
|| [Terminal]

Type

less mysite/settings.py

|| Let us view the '''settings dot py '''file without opening it in the editor.

To do so, type '''less <space> mysite slash settings dot py'''
|-
|| [Terminal]

Highlight INSTALLED_APPS
|| Scroll down.

Except for the '''blog app''', all other '''apps '''have been migrated.

Let us understand this in detail.
|-
|| [Terminal] Press q
|| Press '''q''' to exit from the''' less command.'''
|-
|| [Terminal]

Type ls blog/migrations and press Enter
|| The migration files for each '''app''' will be available in the '''migrations''' folder inside that '''app.'''

Let us now check the '''migrations''' folder in the '''blog app'''.

Type '''ls <space> blog slash migrations'''
|-
|| [Terminal] Highlight output
|| We only see the '''init dot py''' file and there are no migration files.
|-
|| [Terminal]

Type python manage.py makemigrations blog and press Enter
|| Let’s run the '''makemigrations command''' for our '''blog app.'''

Type '''python <space> manage dot py <space> makemigrations <space> blog'''
|-
|| [Terminal]

Point to shell prompt

Highlight

Migrations for 'blog':

blog/migrations/0001_initial.py

- Create model Article

- Create model Blog

- Add field blog to article
|| By running '''makemigrations''', we are telling '''Django''' that we have made some changes to our '''models.'''

'''Django''' will create the initial migrations files based upon your current '''models.'''
|-
|| [Terminal]

ls blog/migrations/
|| Let us check the '''migrations''' folder again.

Type '''ls blog slash migrations slash'''
|-
|| [Terminal]

Highlight

001_initial.py
|| Now we can see that '''001_initial dot py''' file has been created.

'''makemigrations''' will create a new '''migration''' file when there are changes in the '''model.'''
|-
|| [Terminal]

Type python manage.py migrate and press Enter
|| Now, run '''migrate''' again to create those '''model tables '''in your '''database.'''

Type '''python <space> manage dot py <space> migrate'''
|-
|| [Terminal]

Point to the output on the terminal

Highlight

Operations to perform:

Apply all migrations: admin, auth, blog, contenttypes, sessions

Running migrations:

Applying blog.0001_initial... OK
|| Now, we see the command line output for '''migrate.'''

The '''migrate command''' takes all the migrations that haven’t been applied.

|-
|| [Terminal]

Type ls and press Enter
|| Now type '''ls''' and press '''Enter'''.
|-
|| [Terminal]

Highlight db.sqlite3
|| We can see that '''Django''' automatically created an '''SQLite''' '''database''' file, by default.

This is because in '''settings '''it is specified by default.
|-
|| [Terminal]
Type less mysite/settings.py
|| Let us check this.

Type '''less mysite slash settings dot py'''
|-
|| [Terminal]

Highlight DATABASES

Highlight default

Highlight ENGINE sqlite3

Highlight NAME db.sqlite3
|| Scroll down.

Under '''DATABASE, '''we can see

'''default connection'''

'''ENGINE '''as''' sqlite3'''

'''NAME '''as''' db dot sqlite3'''
|-
|| [Terminal]

Press q
|| Press '''q''' to exit from the '''less command.'''
|-
||
|| We will understand '''migrations''' better in the upcoming tutorials of this series.

So for now, we have learnt to create '''models''' within the '''blog web application'''.
|-
|| Type deactivate [Enter]
|| Let us deactivate the '''virtual environment '''now'''.'''

To do so, type '''deactivate''' and press '''Enter'''.
|-
||
|| With this, we come to the end of this tutorial.

Let us summarize.
|-
|| Slide: Summary
|| In this tutorial, we have learnt to

* Create a '''blog app'''
* Initialize a '''Django app'''
* Create a '''Django Model '''and
* Perform '''Database''' migration

|-
|| Slide: Assignment
|| Assignment,

* Create '''models''' under the '''blog app''' in '''demo_project'''
* Perform '''database''' migrations for the '''models '''created

|-
|| Slide: About Spoken Tutorial project
|| The video at the following link summarises the Spoken Tutorial project.

Please download and watch it.
|-
|| Slide: Spoken Tutorial workshops
|| The '''Spoken Tutorial Project''' team conducts workshops and gives certificates.

For more details, please write to us.
|-
|| Slide: Forum for specific questions:
|| Please post your timed queries in this Forum.
|-
|| Slide: FOSSEE to answer questions
|| Please post your general or technical questions in this Forum.
|-
|| Slide: Acknowledgement
|| Spoken Tutorial Project is funded by NMEICT, MHRD, Government of India.

More information on this mission is available at this link.
|-
|| Slide: Thanks Slide
|| This script has been contributed by Thiagarajar College of Engineering and the FOSSEE Project, IIT Bombay.

The video has been recorded by Praveen from Spoken Tutorial Project, IIT Bombay.

Thanks for watching.
|-
|}

@@ Line 37: / Line 37: @@
 |-
 || Slide: Django App
-|| * A '''Django project''' typically contains one or more '''apps'''
+||
 * A '''Django app''' performs a particular task
 * A '''Django app''' will have one or more '''models'''

@@ Line 96: / Line 96: @@
 Type python manage.py startapp blog and press Enter
-|| For this demo, let us create a '''blogging app''' named ''''blog''''.*
+|| For this demo, let us create a '''blogging app''' named ''''blog''''.
 So type '''python <space> manage dot py <space> startapp <space> blog'''
@@ Line 124: / Line 124: @@
 views.py
-|| startproject command creates a project consisting of a file structure as shown here
+|| '''startproject''' command creates a '''project''' consisting of a file structure as shown here.
 |-
 || [Terminal]
-|| Switch back to '''terminal.'''
+|| Switch back to the '''terminal.'''
 |-
 || [Terminal]
@@ Line 175: / Line 175: @@
 Point to INSTALLED_APPS
-|| Locate the line '''INSTALLED_APPS.'''
+|| Locate the line '''INSTALLED UNDERSCORE APPS.'''
-Let us add the '''app config '''line at the beginning of the '''INSTALLED_APPS''' value.
+Let us add the '''app config '''line at the beginning of the '''INSTALLED UNDERSCORE APPS''' value.
 |-
 || [settings.py]
@@ Line 266: / Line 266: @@
 Highlight (auto_now_add=True)
-|| The '''auto_now_add''' will set the very first creation time of the object.
+|| The '''auto underscore now underscore add''' will set the very first creation time of the object.
 |-
 || [models.py] Type:
@@ Line 288: / Line 288: @@
 Highlight models.ForeignKey
-|| Here '''models.ForeignKey''' is a link to another '''model.'''
+|| Here '''models dot ForeignKey''' is a link to another '''model.'''
 This will create an '''object''' that has a many-to-one relationship.
@@ Line 297: / Line 297: @@
 || A many-to-one relationship requires two positional '''arguments.'''
-The '''class''' to which the '''model''' is related and the '''on_delete''' option.
+The '''class''' to which the '''model''' is related and the '''on underscore delete''' option.
 |-
 || [models.py]
@@ Line 304: / Line 304: @@
 on_delete=models.CASCADE
-|| '''on_delete argument''' is required when adding a '''ForeignKey field.'''
+|| '''on underscore delete argument''' is required when adding a '''ForeignKey field.'''
 In''' SQL '''there is constraint named '''ON DELETE CASCADE.'''
@@ Line 322: / Line 322: @@
 models.DateTimeField(auto_now_add=True)
-|| Similar to the '''Blog Model''', '''created_on''' creates the '''DateTimeField''' for the '''Article''' '''model'''.
+|| Similar to the '''Blog Model''', '''created underscore on''' creates the '''DateTimeField''' for the '''Article''' '''model'''.
 |-
 || [models.py]
@@ Line 366: / Line 366: @@
 For '''help''', type
-'''python manage dot py <space> hyphen hyphen help'''
+'''python <space> manage dot py <space> hyphen hyphen help'''
 |-
 || [Terminal]
@@ Line 388: / Line 388: @@
 || '''migrate''' applies the changes noted during the '''makemigrations''' phase.
 |-
-|| [Terminal]
+|| [Terminal] Clear
 Type python manage.py migrate and press Enter
-|| Now, type
+|| Clear the '''terminal'''.
@@ Line 412: / Line 414: @@
 admin, auth, contenttypes, session
-|| The '''migrate command''' will only run migrations for the '''apps '''in '''INSTALLED_APPS.'''
+|| The '''migrate command''' will only run migrations for the '''apps '''in '''INSTALLED UNDERSCORE APPS.'''
 |-
@@ Line 472: / Line 474: @@
 - Add field blog to article
 || By running '''makemigrations''', we are telling '''Django''' that we have made some changes to our '''models.'''
 '''Django''' will create the initial migrations files based upon your current '''models.'''
@@ Line 480: / Line 483: @@
 || Let us check the '''migrations''' folder again.
-Type '''ls blog slash migrations slash'''
+Type '''ls <space> blog slash migrations'''
 |-
 || [Terminal]
@@ Line 487: / Line 490: @@
 _initial.py
-|| Now we can see that '''001_initial dot py''' file has been created.
+|| Now we can see that '''001 underscore initial dot py''' file has been created.
-'''makemigrations''' will create a new '''migration''' file when there are changes in the '''model.'''
+'''makemigrations''' will create a new '''migration''' file when there are changes in the '''module.'''
 |-
 || [Terminal]
@@ Line 496: / Line 499: @@
 || Now, run '''migrate''' again to create those '''model tables '''in your '''database.'''
 |-
 || [Terminal]
@@ Line 511: / Line 513: @@
 Applying blog.0001_initial... OK
-|| Now, we see the command line output for '''migrate.'''
+|| Now, we see the '''command line''' output for '''migrate.'''
 The '''migrate command''' takes all the migrations that haven’t been applied.
@@ Line 524: / Line 526: @@
 Highlight db.sqlite3
-|| We can see that '''Django''' automatically created an '''SQLite''' '''database''' file, by default.
+|| We can see that '''Django''' automatically created an '''SQLite database''' file, by default.
-This is because in '''settings '''it is specified by default.
+This is because in '''settings, '''it is specified by default.
 |-
 || [Terminal]
@@ Line 547: / Line 549: @@
 Under '''DATABASE, '''we can see
-'''default connection'''
+*'''default connection'''
-'''ENGINE '''as''' sqlite3'''
+*'''ENGINE '''as''' sqlite3'''
-'''NAME '''as''' db dot sqlite3'''
+*'''NAME '''as''' db dot sqlite3'''
 |-
 || [Terminal]
@@ Line 561: / Line 563: @@
 || We will understand '''migrations''' better in the upcoming tutorials of this series.
-So for now, we have learnt to create '''models''' within the '''blog web application'''.
+So far, we have learnt to create '''models''' within the '''blog web application'''.
 |-
 || Type deactivate [Enter]
-|| Let us deactivate the '''virtual environment '''now'''.'''
+|| Let us deactivate the '''virtual environment '''now.
 To do so, type '''deactivate''' and press '''Enter'''.