The following is the command to create application.

python manage.py startapp firstApp 

D:djangoprojectsfirstProject>python manage.py startapp firstApp 

The following is the folder structure got created. 

D:djangoprojects> 

└───firstProject 

      │ db.sqlite3 

      │ manage.py 

      │ 

     ├───firstApp 

      │    │ admin.py 

      │    │ apps.py 

      │    │ models.py 

      │    │ tests.py 

      │    │ views.py 

      │    │ __init__.py 

      │   │ 

     │   └───migrations 

     │              __init__.py 

     │ 

     │ 

    └───firstProject 

         │ settings.py 

         │ urls.py 

         │ wsgi.py 

         │ __init__.py 

     In this file we have to specify test functions to test our code. 

Activity-1: Add our application in settings.py,so that Django aware about our application.

In settings.py:

Activity-2: Create a view for our application in views.py.

. View is responsible to prepare required response to the end user. i.e view contains

  business logic.

. There are 2 types of views.

     1). Function Based Views

      2) . Class Based Views

. In this application we are using Function based views. 

View can accept request as input and perform required operations and provide proper

response to the end user.

Activity-3: Define url-pattern for our view in urls.py file.

. This url-pattern will be used by end-user to send request for our views.

. The ‘urlpatterns’ list routes URLs to views.

For functional views we have to do the following 2 activities:

Add an import: from firstApp import views

Add a URL to urlpatterns: url(r’^greeting/’, views.display)

Whenever end user sending the request with urlpattern: greeting then disply() function

will be executed and provide required response.

Activity-4: Start Server and Send the request

                       python manage.py runserver 

                        http://127.0.0.1:8000/greetings 

Http Request flow in Django Application: 

1. Whenever end user sending the request first Django development server will get that

   request.

2. From the Request django will identify urlpattern and by using urls.py, the

    corresponding view will be identified.

3. The request will be forwared to the view. The corresponding function will be executed

    and provide required response to the end user. 

Summary of Sequence of Activities related to

Django Project: 

1) Creation of Django project

   django-admin startproject firstProject

2) Creation of Application in that project

    py manage.py startapp firstApp

3) Add application to the Project

   (inside settings.py)

4) Define view function inside views.py

5) Define url-pattern for our view inside urls.py

6) Start Server

    py manage.py runserver 

7) Send the request

How to change  Django Server Port: 

 

By default Django develoment server will run on port number: 8000. But we can change

port number based on our requirement as follows.

Now Server running on port number: 7777

We have to send the request with this port number only

http://127.0.0.1:7777/greetings/

http://127.0.0.1:8000/time/ 

Various Practice Applications:

1. Write Django Application just to send Helloworld message as response.

2. Write Django application to send server time as response

3. Single application with multiple views 

views.py:

1) from django. shortcuts import render

2) from django. httpimport Http Response

3) #Createyourviewshere.

4) def good_morning_view(request):

5)       return HttpResponse(‘<h1>Hello Friend Good Morning!!!</h1>’)

6) def good_evening_view(request):

7)        return HttpResponse(‘<h1>Hello Friend Good Evening !!!</h1>’)

8) def good_afternoon_view(request):

9)        return HttpResponse(‘<h1>Hello Friend Good Afternoon!!!</h1>’)

urls.py

1) from django .conf .urls import url

2) from django .contrib import admin

3) from test app import views

4) urlpatterns=[

5) url(r‘^admin/’, admin.site.urls),

6) url(r‘^morning/’, views.good_morning_view),

7) url(r‘^afternoon/’, views.good_afternoon_view),

8) url(r‘^evening/’, views.good_evening_view),

 . Single project with multiple applications:

greetingapp: views.py

1) from django .shortcuts import render

2) from django .http import HttpResponse

3) #Create your viewshere.

4) def greetings_view(request):

5) #total html code 1000 lines of code

6)      return HttpResponse(‘<h1>Hello Friends Good Morning…Have a Nice Day</h1’)

timeapp:views.py

1) from django .shortcuts import render

2) from django .httpi mport HttpResponse

3) import datetime

4) #Create yourv iewshere.

5) def time_info_view(request):

6)     time= datetime.datetime.now()

7)     s=‘<h1>Hello Current Date and Time is :’+str(time)+‘</h1>’

8)     return HttpResponse(s)

Issue with urls.py

1) from greeting app import views

2) from timeapp import views

Take special care while defining url patterns.we will get error b’z only one views.py is

available. But we can solve this problem with any of the following 2 ways

First Approach

1) from greetingapp .views import greetings_view

2) from timeapp .views import time_info_view

3) urlpatterns=[

4) url(r‘^admin/’, admin.site.urls),

5) url(r‘^greetings/’,greetings_view),

6) url(r‘^time/’,time_info_view), Second Approach 1) from. greetingapp import viewsasv1 2) from timeapp import viewsasv2 3) urlpatterns=[ 4) url(r‘^admin/’, admin.site.urls), 5) url(r‘^greetings/’,v1.greetings_view), 6) url(r‘^time/’,v2.time_info_view),  ] Q. Is it possible to define mutlitple url patterns for the same view function? Answer: Yes, by using the following approach 1) urlpatterns=[ 2) url(r‘^admin/’, admin.site.urls), 3) url(r‘^$’, views.wish), 4) url(r‘^test/’, views.wish)  ] http://127.0.0.1:8000/ http://127.0.0.1:8000/test  Demo Application:  1. Creation of Project     django-admin startproject urlProject  2. Creation of Application    py manage.py startapp testapp  3. Add our application to the Project inside settings.py file      INSTALLED_APPS=[                   ………                 ‘testapp’                  ]  4. Define View Function in views.py

views.py 

1) from django .shortcuts import render

2) from django .http import HttpResponse

3) #Create your views here.

4) def first_view(request):

5) return HttpResponse(‘<h1>Response from First View</h1>’)

6) def second_view(request):

7) return HttpResponse(‘<h1>Response from Second View</h1>’)

8) def third_view(request):

9) return HttpResponse(‘<h1>Response from third View</h1>’)

10) def fourth_view(request):

11) return HttpResponse(‘<h1>Response from Fourth View</h1>’)

12) def fifth_view(request):

13) return HttpResponse(‘<h1>Response from Fifth View</h1>’) 5. Create a seperate urls.py file inside application

testapp/urls.py

1) from django .conf .urls import url

2) from testapp import views 3) urlpatterns=[ 4) url(r‘^first/’, views.first_view), 5) url(r‘^second/’, views.second_view), 6) url(r‘^third/’, views.third_view), 7) url(r‘^fourth/’, views.fourth_view), 8) url(r‘^fifth/’, views.fifth_view),  ] . Include this application level urls.py inside project level urls.py file. . from django.conf.urls. import include  project level:urls.py 1) from django .conf .urls import url ,include 2) from django .contrib import admin 3) urlpatterns=[ 4) url(r‘^admin/’, admin.site.urls), 5) url(r‘^testapp/’, include(‘testapp.urls’)),  ] . Run Server py manage.py runserver . Send Request http://127.0.0.1:8000/urlApp/test Note: We can see reusability of application in other project just with only 2 lines addition 1. settings.py –>add application name 2. urls.py —>just add: url(r’^urlApp/’,include(‘urlApp.urls’),  Advantages: The main advantages of defining urlpatterns at application level instead of project level are 1) 2) It promotes reusability of Django Applications across multiple projects Project level urls.py file will be clean and more readable