Django Development time helper notes

django-helper.txt

kill port already defined
=========================

	fuser -k 8000/tcp

	Kill annd Restart whenever u added new apps

---------------------------------------------

Create and activate virtual environment
========================================

  	pip install virtualenv

  	pip freeze

  	virtualenv ecitvenv

  	[root@ws26 ecitvenv]# source bin/activate


----------------------------------------------

Creating a project
==================

 	django-admin startproject projectname

--------------------------------------

run command
===========

	python manage.py runserver 8001

	python manage.py runserver 103.231.43.193:9000

---------------------------

Create app
==========

	python manage.py startapp appname

--------------------------------

Import a package
================

	from django.http import HttpResponse

	from . import views

--------------------------------

url settings
============

from django.conf.urls import url

from . import views

urlpatterns = [
url(r'^$', views.index, name='index'),
]

-------------------------

include url 
===========

from django.conf.urls import include, url
from . import views   // views module from current app

urlpatterns = [
url(r'^polls/', include('polls.urls')),
url(r'^$', views.index, name='index'), // for example home page
url(r'^(?P<pkcolumn>[0-9]+)/$', views.detail, name='detail'),  // ex: /polls/5/
url(r'^(?P<pkcolumn>[0-9]+)/results/$', views.results, name='results'),  // /polls/5/results/
]



----------------------------------------

Database settings
=================

DATABASES = {
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        'NAME': 'eaglesoft',
        'USER':  'siva',
        'PASSWORD' : 'siva098'
    }
}

---------------------------------

migrations command
==================

python manage.py migrate

python manage.py makemigrations then use above command if model modified 


Install an app in settings
==========================

INSTALLED_APPS = [
    ...
    'customer',
    'salesperson',
    'serviceprovider',
    ...
]

--------------------------------

Create a model
==============

from django.db import models

class Question(models.Model):
   fields

--------------------------------

Create a foriegn key relationship
=================================

class Choice(models.Model):
 question = models.ForeignKey(Question, on_delete=models.CASCADE)

---------------------------------

Open shell prompt
=================

	python manage.py shell

------------------------

add current time in database field while saving
===============================================

	from django.utils import timezone
    q = Question(question_text="What's new?", pub_date=timezone.now())

------------------------------------------------

get primary key after saving
============================

  q.save()
  q.id // saved pk

----------------------------

fetch all model data
====================

	Question.objects.all()

--------------------------

String representation of model for easy view and learning
=========================================================

	class Question(models.Model):
	
		def __str__(self):
		return self.question_text	      	 

---------------------------------------------------------

Create custom function in model
===============================

	class User(models.Model):
		def fullname(self):
		return self.first_name + self.last_name

------------------------------------

Filter a model based attribute
==============================

Question.objects.filter(id=1)
Question.objects.filter(question_text__startswith='What')
Question.objects.get(pk=1)

-------------------------------

Call custom function of a model
===============================

	q = User.objects.get(pk=1)
    q.fullname()	

--------------------------------

Fetch related model data
========================

 q = Question.objects.get(pk=1)
 q.choice_set.all()

 -----------------------------

 Save related models at a time
 =============================

 	q = Question(question_text="What's new?", pub_date=timezone.now())

 	q.save()

 	q.choice_set.create(choice_text='Not much', votes=0)

 	q.choice_set.count() // get count

 	q.delete() // for delete

 --------------------------------------
 
 Creating an admin user
 ======================

 	python manage.py createsuperuser

------------------------------------

Show the apps model in admin backend
====================================
	in appsdirectory/admin.py

	from django.contrib import admin
	from .models import Question
	admin.site.register(Question) 		

--------------------------------------

Model order by fetching
=======================

	from django.http import HttpResponse
	from .models import Question

	def index(request):
		latest_question_list = Question.objects.order_by('-pub_date')[:5]
		output = ', '.join([q.question_text for q in latest_question_list])
		return HttpResponse(output)

 it can be accessed in template like below,

   polls/templates/polls/index.html

  {% if latest_question_list %}
		<ul>
		{% for question in latest_question_list %}
		<li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>
		{% endfor %}
		</ul>
  {% else %}
		<p>No polls are available.</p>
  {% endif %}		

--------------------------------------------

Exception and Raising a 404 error
=================================

	from django.http import Http404
	from django.shortcuts import render
	from .models import Question

	def detail(request, question_id):
		try:
			question = Question.objects.get(pk=question_id)
		except Question.DoesNotExist:
			raise Http404("Question does not exist")
		return render(request, 'polls/detail.html', {'question': question})

	in polls/templates/polls/detail.html
	
	   {{ question }}

	Alternative method
	
	from django.shortcuts import get_object_or_404, render
	from .models import Question

	def detail(request, question_id):
		question = get_object_or_404(Question, pk=question_id)
		return render(request, 'polls/detail.html', {'question': question}) 

---------------------------------------------------------------------------


Using for loop in views
========================

	<h1>{{ question.question_text }}</h1>
	<ul>
	{% for choice in question.choice_set.all %}
	<li>{{ choice.choice_text }}</li>
	{% endfor %}
	</ul>		 	

----------------------------------------------	

Url link to show view by passing pkey
=====================================

	<li><a href="/polls/{{ question.id }}/">{{ question.question_text }}</a></li>
	<li><a href="{% url 'detail' question.id %}">{{ question.question_text }}</a></li>

	set app name

		app_name = 'polls'
		urlpatterns = [
			url(r'^$', views.index, name='index'),
			url(r'^(?P<question_id>[0-9]+)/$', views.detail, name='detail'),
			url(r'^(?P<question_id>[0-9]+)/results/$', views.results, name='results'),
			url(r'^(?P<question_id>[0-9]+)/vote/$', views.vote, name='vote'),
			]

		then
		
		<li><a href="{% url 'polls:detail' question.id %}">{{ question.question_text }}</a></li>

----------------------------------------------------------------------------------

Write a simple form
===================

polls/templates/polls/detail.html

<h1>{{ question.question_text }}</h1>
{% if error_message %}<p><strong>{{ error_message }}</strong></p>{% endif %}
<form action="{% url 'polls:vote' question.id %}" method="post">
{% csrf_token %}
{% for choice in question.choice_set.all %}
<input type="radio" name="choice" id="choice{{ forloop.counter }}" value="{{ choice.id }}" />
<label for="choice{{ forloop.counter }}">{{ choice.choice_text }}</label><br />
{% endfor %}
<input type="submit" value="Vote" />
</form>


url for generic views 
=====================

	urlpatterns = [
	url(r'^$', views.IndexView.as_view(), name='index'),
	url(r'^(?P<pk>[0-9]+)/$', views.DetailView.as_view(), name='detail'),
	url(r'^(?P<pk>[0-9]+)/results/$', views.ResultsView.as_view(), name='results'),
	url(r'^(?P<question_id>[0-9]+)/vote/$', views.vote, name='vote'),
	]

------------------------------------------------

Generic view custom query set
=============================

	class IndexView(generic.ListView):
		template_name = 'polls/index.html'
		context_object_name = 'latest_question_list'

		def get_queryset(self):
			"""Return the last five published questions."""
			return Question.objects.order_by('-pub_date')[:5]	

-------------------------------------------------

Adding static files ( css , js , image ) into our app's template
================================================================

polls/static/polls/style.css

{% load static %}
<link rel="stylesheet" type="text/css" href="{% static 'polls/style.css' %}" />	 		

model object to string for learning
===================================

def __str__(self):
    	return self.status_desc

-----------------------------------    	

Create custom permission example
================================

class Task(models.Model):
    ...
    class Meta:
        permissions = (
            ("view_task", "Can see available tasks"),
            ("change_task_status", "Can change the status of tasks"),
            ("close_task", "Can remove a task by setting its status as closed"),
        )


---------------------------------

Check user has a permission
===========================

user.has_perm('app.view_task')

-----------------------------

Block of content inside a template
===================================

{% extends "base.html" %}
{% block content %}
<h2>Publishers</h2>
<ul>
{% for publisher in object_list %}
<li>{{ publisher.name }}</li>
{% endfor %}
</ul>
{% endblock %}

-------------------------------------

Generic view custom query 
=========================

from django.views.generic import ListView
from books.models import Book

class BookList(ListView):
queryset = Book.objects.order_by('-publication_date')

------------------------------------------

Filter based current user in generic view
=========================================

from django.shortcuts import get_object_or_404
from django.views.generic import ListView
from books.models import Book, Publisher


class PublisherBookList(ListView):
template_name = 'books/books_by_publisher.html'
def get_queryset(self):
self.publisher = get_object_or_404(Publisher, name=self.args[0])
return Book.objects.filter(publisher=self.request.user)

---------------------------------------------

URL Redirection after delete
========================

class AuthorDelete(DeleteView):
model = Author
success_url = reverse_lazy('author-list')

------------------------------------------------

fetch objects that are created by specific user
===============================================

from django.contrib.auth.models import User
from django.db import models

class Author(models.Model):
name = models.CharField(max_length=200)
created_by = models.ForeignKey(User, on_delete=models.CASCADE)     

from django.views.generic.edit import CreateView
from myapp.models import Author

class AuthorCreate(CreateView):
model = Author
fields = ['name']
def form_valid(self, form):
form.instance.created_by = self.request.user
return super(AuthorCreate, self).form_valid(form)   

---------------------------------------------------

CreateView with ajax example
============================

from django.http import JsonResponse
from django.views.generic.edit import CreateView
from myapp.models import Author
class AjaxableResponseMixin(object):
"""
Mixin to add AJAX support to a form.
Must be used with an object-based FormView (e.g. CreateView)

"""

def form_invalid(self, form):
response = super(AjaxableResponseMixin, self).form_invalid(form)
if self.request.is_ajax():
return JsonResponse(form.errors, status=400)
else:
return response

def form_valid(self, form):
# We make sure to call the parent's form_valid() method because
# it might do some processing (in the case of CreateView, it will
# call form.save() for example).
response = super(AjaxableResponseMixin, self).form_valid(form)
if self.request.is_ajax():
data = {
'pk': self.object.pk,
}
return JsonResponse(data)
else:
return response

class AuthorCreate(AjaxableResponseMixin, CreateView):
model = Author
fields = ['name']

-----------------------------------------------------------------------

ListView with builtin pagination
================================

{% extends "base.html" %}
{% block content %}
<h2>Publisher {{ publisher.name }}</h2>
<ol>
{% for book in page_obj %}
<li>{{ book.title }}</li>
{% endfor %}
</ol>


<div class="pagination">
<span class="step-links">
{% if page_obj.has_previous %}
<a href="?page={{ page_obj.previous_page_number }}">previous</a>
{% endif %}
<span class="current">
Page {{ page_obj.number }} of {{ paginator.num_pages }}.
</span>
{% if page_obj.has_next %}
<a href="?page={{ page_obj.next_page_number }}">next</a>
{% endif %}
</span>
</div>
{% endblock %}

------------------------------------------

File uploads
============

from django.db import models

class Car(models.Model):
name = models.CharField(max_length=255)
price = models.DecimalField(max_digits=5, decimal_places=2)
photo = models.ImageField(upload_to='cars')

>>> car = Car.objects.get(name="57 Chevy")
>>> car.photo
<ImageFieldFile: chevy.jpg>
>>> car.photo.name
'cars/chevy.jpg'
>>> car.photo.path
'/media/cars/chevy.jpg'
>>> car.photo.url
'http://media.example.com/cars/chevy.jpg'

-----------------------------------------------------

Access value from .settings.py
==============================

from django.conf import settings

 new_path = settings.MEDIA_ROOT

----------------------------------------------------

Sending emails with 
===================

from django.core.mail import send_mail
send_mail('Subject here', 'Here is the message.', 'from@example.com',
['to@example.com'], fail_silently=False)

---------------------------------------------------------

logging
=======

# import the logging library
import logging
# Get an instance of a logger
logger = logging.getLogger(__name__)
def my_view(request, arg1, arg):
...
if bad_mojo:
# Log an error message
logger.error('Something went wrong!')

------------------------------------------------------------

Configuring static files
========================

django.contrib.staticfiles in installed apps

STATIC_URL = '/static/'

{% load static %}
<img src="{% static "my_app/myexample.jpg" %}" alt="My image"/>

----------------------------------------------------------------

Reverse lazy URL
================

from django.views.generic.edit import DeleteView
from django.urls import reverse_lazy
from myapp.models import Author
class AuthorDelete(DeleteView):
model = Author
success_url = reverse_lazy('author-list')

------------------------------------------------------------------

Adding new column with custom function in admin list
====================================================

from django.contrib import admin
from myapp.models import Article
def make_published(modeladmin, request, queryset):
queryset.update(status='p')
make_published.short_description = "Mark selected stories as published"

class ArticleAdmin(admin.ModelAdmin):
list_display = ['title', 'status']
ordering = ['title']
actions = [make_published]
admin.site.register(Article, ArticleAdmin)

---------------------------------------------------

Custom Message after result in custom admin list
===============================================

class ArticleAdmin(admin.ModelAdmin):
...
def make_published(self, request, queryset):
rows_updated = queryset.update(status='p')
if rows_updated == 1:
message_bit = "1 story was"
else:
message_bit = "%s stories were" % rows_updated
self.message_user(request, "%s successfully marked as published." % message_bit)

----------------------------------------------------------------------------

Jquery Ajax Post
================

<script src="{% static 'student/jquery.js' %}"></script>
	<script>
			function getCookie(name) {
		    var cookieValue = null;
		    if (document.cookie && document.cookie != '') {
		        var cookies = document.cookie.split(';');
		        for (var i = 0; i < cookies.length; i++) {
		            var cookie = cookies[i];
		            // Does this cookie string begin with the name we want?
		            if (cookie.substring(0, name.length + 1) == (name + '=')) {
		                cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
		                break;
		            }
		        }
		    }
		    return cookieValue;
		}
		var csrftoken = getCookie('csrftoken');
	</script>
	<script type="text/javascript">
$(document).ready(function() {
    
        
        var data = {
            'foo': 'bar'
        }

        $.ajaxSetup({
		    beforeSend: function(xhr, settings) {
		        if (!(/^http:.*/.test(settings.url) || /^https:.*/.test(settings.url))) {
		            // Only send the token to relative URLs i.e. locally.
		            xhr.setRequestHeader("X-CSRFToken", csrftoken);
		        }
		    }
		});

        $.ajax({
			    "type": "POST",
			    "dataType": "json",
			    "url": "/student/create/",
			    "data": data,
			    "beforeSend": function(xhr, settings) {
			        console.log("Before Send");
			        $.ajaxSettings.beforeSend(xhr, settings);
			    },
			    "success": function(result) {
			        console.log(result);
			    }
			})
    
});
</script>

in views
........

from django.shortcuts import render
from django.http import HttpResponse
from django.http import JsonResponse
from .models import Student

def create(request):
	if(request.method=='POST'): 
		return JsonResponse(request.POST)
	else :
	    return render(request,'student/create.html')


-------------------------------------------------------------------

Angularjs Ajax POST example
===========================

<script>
		function getCookie(name) {
	    var cookieValue = null;
	    if (document.cookie && document.cookie != '') {
	        var cookies = document.cookie.split(';');
	        for (var i = 0; i < cookies.length; i++) {
	            var cookie = cookies[i];
	            // Does this cookie string begin with the name we want?
	            if (cookie.substring(0, name.length + 1) == (name + '=')) {
	                cookieValue = decodeURIComponent(cookie.substring(name.length + 1));
	                break;
	            }
	        }
	    }
	    return cookieValue;
	}
	var csrftoken = getCookie('csrftoken');
	
	var app = angular.module('Student',[])
	app.config(function($httpProvider){
		$httpProvider.interceptors.push('httpRequestInterceptor');
	})
	app.factory('httpRequestInterceptor',
			['$rootScope', function($rootScope)
			 {
			  return {
			   request: function($config) {
			       $config.headers['X-CSRFToken'] = csrftoken;
			       $config.headers['Content-Type'] = 'application/x-www-form-urlencoded'
			   
			  return $config;
			  }
			 };
			}]);

	app.controller('StudentController',function($scope,$http){

		$scope.message = 'Hello'

		$scope.save = function(){

			var data = {
				name : "Siva via ajax"
			}
			
			$http({
			    method: 'POST',
			    url: '/student/create/',
			    data: $.param(data)
			}).then(function(response){
				console.log(response.data,'data')
			})
		}
	})
	</script>

in template
...........

{% extends "student/base.html" %}
{% block content %}
<div ng-controller="StudentController">
	<form action="">
	{% csrf_token %}
		<input type="text" name="name">
		<button ng-click="save()">Save</button>	
	</form>

	<p ng-bind="message"></p>
</div>

{% endblock %}

in views
........

from django.shortcuts import render
from django.http import HttpResponse
from django.http import JsonResponse
from .models import Student

import json

def create(request):
	if(request.method=='POST'):
		s = Student(student_id=request.POST['student_id'],name=request.POST['name'])
		s.save() 
		return JsonResponse(request.POST)
	else :
	    return render(request,'student/create.html')

def list(request):
	context = { 'lists' : Student.objects.all() } 
	return render(request,'student/list.html',context)


-------------------------------------------------------------

make links with anchor tag example
==================================

from django.conf.urls import url
from . import views

urlpatterns = [
    url(r'^$', views.list,name="list"),
    url(r'^create/', views.create,name="create"),
    
]


in base template file
.....................

<li><a href="{% url 'create' %}">Create</a></li>
<li><a href="{% url 'list' %}">List</a></li>

---------------------------------------------------------------

Pagination without using ListView
=================================

from django.shortcuts import render
from django.http import HttpResponse
from django.http import JsonResponse
from django.core.paginator import Paginator, EmptyPage, PageNotAnInteger
from .models import Student

import json

def create(request):
	if(request.method=='POST'):
		s = Student(student_id=request.POST['student_id'],name=request.POST['name'])
		s.save() 
		return JsonResponse(request.POST)
	else :
	    return render(request,'student/create.html')

def list(request):
	student_list = Student.objects.all()
	paginator = Paginator(student_list, 5)
	page = request.GET.get('page')
	try:
		lists = paginator.page(page)
	except PageNotAnInteger:
	# If page is not an integer, deliver first page.
		lists = paginator.page(1)
	except EmptyPage:
	# If page is out of range (e.g. 9999), deliver last page of results.
		lists = paginator.page(paginator.num_pages)
	return render(request, 'student/list.html', {'lists': lists})


in views
........

{% extends "student/base.html" %}
{% block content %}

{% for list in lists %}
<p>{{ list.name | lower }}</p>

{% endfor %}

<div class="pagination">
<span class="step-links">
{% if lists.has_previous %}
<a href="?page={{ lists.previous_page_number }}">previous</a>
{% endif %}
<span class="current">
Page {{ lists.number }} of {{ lists.paginator.num_pages }}.
</span>
{% if lists.has_next %}
<a href="?page={{ lists.next_page_number }}">next</a>
{% endif %}
</span>
</div>

{% endblock %}

------------------------------------------------------------------

Pagination and search field customization is Admin nd hide filter
=================================================================

from django.contrib import admin

# Register your models here.
from .models import Student



class StudentAdmin(admin.ModelAdmin):
	fields = ['name']
	#list_filter = ['name']
	search_fields = ['name']
	list_per_page = 5
	
admin.site.register(Student, StudentAdmin)

--------------------------------------------------------

 
Json response for models
========================
from django.core import serializers

def nglist(request):
	return HttpResponse(serializers.serialize("json",Student.objects.all()))

----------------------------------------------------------

angular ng-repeat example inside views
======================================

<ul>
		<li ng-repeat="dat in data">
		<span ng-bind="dat.fields.name"></span>
		</li>
	</ul>

------------------------------------------

Return Errors and page not found
================================

from django.http import HttpResponse, HttpResponseNotFound
def my_view(request):
# ...
if foo:
return HttpResponseNotFound('<h1>Page not found</h1>')
else:
return HttpResponse('<h1>Page was found</h1>')

---------------------------------------------------------


Exception Handling Example
==========================

from django.http import Http404
from django.shortcuts import render
from polls.models import Poll
def detail(request, poll_id):
try:
p = Poll.objects.get(pk=poll_id)
except Poll.DoesNotExist:
raise Http404("Poll does not exist")
return render(request, 'polls/detail.html', {'poll': p})

-----------------------------------------------