Ans: Django is a web framework in python to develop a web application in python.
Django is a free and open source web application framework, written in Python.
Ans: Features available in Django are
Ans: Django architecture consists of
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Ans: To start a project in Django, you use command $ django-admin.py and then use the command
Project
_init_.py
manage.py
settings.py
urls.py
Ans: You can use the command edit mysite/setting.py , it is a normal python module with module level representing Django settings.
Django uses SQLite by default; it is easy for Django users as such it won’t require any other type of installation. In the case your database choice is different that you have to the following keys in the DATABASE ‘default’ item to match your database connection settings
If you are not choosing SQLite as your database then setting like Password, Host, User, etc. must be added.
Ans: Views are Django functions that take a request and return a response. To write a view in Django we take a simple example of “Guru99_home” which uses the template Guru99_home.html and uses the date-time module to tell us what the time is whenever the page is refreshed. The file we required to edit is called view.py, and it will be inside mysite/myapp/
Copy the below code into it and save the file
from datatime import datetime
from django.shortcuts import render
def home (request):
return render(request, ‘Guru99_home.html’, {‘right_now’: datetime.utcnow()})
Once you have determined the VIEW, you can uncomment this line in urls.py
# url ( r ‘^$’ , ‘mysite.myapp.views.home’ , name ‘Guru99’),
The last step will reload your web app so that the changes are noticed by the web server.
Ans: There are three main things required to set up static files in Django
Ans: The template is a simple text file. It can create any text-based format like XML, CSV, HTML, etc. A template contains variables that get replaced with values when the template is evaluated and tags (% tag %) that controls the logic of the template.
Ans: In Django, the session framework enables you to store and retrieve arbitrary data on a per-site-visitor basis. It stores data on the server side and abstracts the receiving and sending of cookies. Session can be implemented through a piece of middleware.
Ans: To use file based session you have to set the SESSION_ENGINE settings to “django.contrib.sessions.backends.file”
Ans: Migration in Django is to make changes to your models like deleting a model, adding a field, etc. into your database schema. There are several commands you use to interact with migrations.
To do the migration in SQL, you have to print the SQL statement for resetting sequences for a given app name.
django-admin.py sqlsequencreset
Use this command to generate SQL that will fix cases where a sequence is out sync with its automatically incremented field data.
Ans: To load data into Django you have to use the command line Django-admin.py loaddata. The command line will searches the data and loads the contents of the named fixtures into the database.
Ans: This command line executes over the entire source tree of the current directory and abstracts all the strings marked for translation. It makes a message file in the locale directory.
Ans: In Django, there is three possible inheritance styles
Ans: Field class types determines
Ans: Template can create formats like XML,HTML and CSV(which are text based formats). In general terms template is a simple text file. It is made up of variables that will later be replaced by values after the template is evaluated and has tags which will control template’s logic.
Ans: Some of the typical usage of middlewares in Django are: Session management, user authentication, cross-site request forgery protection, content Gzipping, etc.
Ans: Views will take request to return response. Let’s write a view in Django : “example” using template example.html , using the date-time module to tell us exact time of reloading the page. Let’s edit a file called view.py, and it will be inside randomsite/randomapp/
To do this save and copy following into a file:
Default
from datatime import datetime
from django.shortcuts import render
def home (request):
return render(request, ‘Guru99_home.html’, {‘right_now’: datetime.utcnow()})
Default
You have to determine the VIEW first, and then uncomment this line located in file urls.py
# url ( r ‘^$’ , ‘randomsite.randomapp.views.home’ , name ‘example’),
Ans: This will reload the site making changes obvious.
Keep in mind that it should take an index number and output the sequence. Additionally, there should be a page that shows the most recent generated sequences.
Following is one of the solution for generating fibonacci series:
Default
def fib(n):
"Complexity: O(log(n))"
if n <= 0:
return 0
i = n - 1
(a, b) = (1, 0)
(c, d) = (0, 1)
while i > 0:
if i % 2:
(a, b) = (d * b + c * a, d * (b + a) + c * b)
(c, d) = (c * c + d * d, d * (2 * c + d))
i = i / 2
return a + b
Default
Below is a model that would keep track of latest numbers:
from django.db import models
class Fibonacci(models.Model):
parameter = models.IntegerField(primary_key=True)
result = models.CharField(max_length=200)
time = models.DateTimeField()
DefaultFor view, you can simply use the following code:
from models import Fibonacci
def index(request):
result = None
if request.method=="POST":
try:
n=int(request.POST.get('n'))
except:
return Http404
try:
result = Fibonacci.objects.get(pk=n)
result.time = datetime.now()
except DoesNotExist:
result = str(fib(n))
result = Fibonacci(n, result, datetime.now())
result.save()
return direct_to_template(request, 'base.html', {'result':result.result})
You could use models to get last ‘n’ entities.
Ans: Django runs on MVC architecture. Following are the components that make up django architecture:
Ans: Session framework in django will store data on server side and interact with end-users. Session is generally used with a middle-ware. It also helps in receiving and sending cookies for authentication of a user.
Ans: Yes, you can create singleton object. Here’s how you do it :
Default
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2 3 4 5 |
class Singleton(object):
def __new__(cls,*args,**kwargs): if not hasattr(cls,'_inst'): cls._inst = super(Singleton,cls).__new__(cls,*args,**kwargs) return cls._inst |
Ans: Few caching strategies that are available in Django are as follows:
Ans: There are 3 inheritance types in Django
Ans: If the data is complex and consists of multiple joins using the SQL will be clearer.
If Performance is a concern for your, ORM aren’t your choice. Genrally. Object-relation-mapping are considered good option to construct an optimized query, SQL has an upper hand when compared to ORM.
Ans: There are 7 steps ahead to start Django project.
Step 1: Create project in terminal/shell
f2finterview:~$ django-admin.py startproject sampleproject
Step 2: Create application
f2finterview:~$ cd sampleproject/
f2finterview:~/sampleproject$ python manage.py startapp sampleapp
Step 3: Make template directory and index.html file
f2finterview:~/sampleproject$ mkdir templates
f2finterview:~/sampleproject$ cd templates/
f2finterview:~/sampleproject/templates$ touch index.html
Step 4: Configure initial configuration in settings.py
Add PROJECT_PATH and PROJECT_NAME
import os
PROJECT_PATH = os.path.dirname(os.path.abspath(__file__))
PROJECT_NAME = 'sampleproject'
Add Template directories path
TEMPLATE_DIRS = (
os.path.join(PROJECT_PATH, 'templates'),
)
Add Your app to INSTALLED_APPS
INSTALLED_APPS = (
'sampleapp',
)
Step 5: Urls configuration in urls.py
from django.conf.urls.defaults import patterns, include, url
urlpatterns = patterns('',
url(r'^$', 'sampleproject.sampleapp.views.index', name='index'),
)
Step 6: Add index method in views.py
from django.shortcuts import render_to_response, get_object_or_404
from django.template import RequestContext
def index(request):
welcome_msg = 'Hello World'
return render_to_response('index.html',locals(),context_instance=RequestContext(request))
Step7: Add welcome_msg in index.html
<!DOCTYPE html>
<html>
<body>
<h1>My First Heading For Say...</h1>
<p></p>
</body>
</html>
Ans: Use bellow sample method to login with email or username.
from django.conf import settings
from django.contrib.auth import authenticate, login, REDIRECT_FIELD_NAME
from django.shortcuts import render_to_response
from django.contrib.sites.models import Site
from django.template import Context, RequestContext
from django.views.decorators.cache import never_cache
from django.views.decorators.csrf import csrf_protect
@csrf_protect
@never_cache
def signin(request,redirect_field_name=REDIRECT_FIELD_NAME,authentication_form=LoginForm):
redirect_to = request.REQUEST.get(redirect_field_name, settings.LOGIN_REDIRECT_URL)
form = authentication_form()
current_site = Site.objects.get_current()
if request.method == "POST":
pDict =request.POST.copy()
form = authentication_form(data=request.POST)
if form.is_valid():
username = form.cleaned_data['username']
password = form.cleaned_data['password']
try:
user = User.objects.get(email=username)
username = user.username
except User.DoesNotExist:
username = username
user = authenticate(username=username, password=password)
# Log the user in.
login(request, user)
return HttpResponseRedirect(redirect_to)
else:
form = authentication_form()
request.session.set_test_cookie()
if Site._meta.installed:
current_site = Site.objects.get_current()
else:
current_site = RequestSite(request)
return render_to_response('login.html',locals(), context_instance=RequestContext(request))
Ans: When a user requests a page from your Django-powered site, this is the algorithm the system follows to determine which Python code to execute:
Django determines the root URLconf module to use. Ordinarily, this is the value of the ROOT_URLCONF setting, but if the incoming HttpRequest object has an attribute called urlconf (set by middleware request processing), its value will be used in place of the ROOT_URLCONF setting.
Django loads that Python module and looks for the variable urlpatterns. This should be a Python list, in the format returned by the function django.conf.urls.patterns()
Django runs through each URL pattern, in order, and stops at the first one that matches the requested URL.
Once one of the regexes matches, Django imports and calls the given view, which is a simple Python function (or a class based view). The view gets passed an HttpRequest as its first argument and any values captured in the regex as remaining arguments.
If no regex matches, or if an exception is raised during any point in this process, Django invokes an appropriate error-handling view.
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Messages(models.Model):
message_from = models.ForeignKey(User,related_name="%(class)s_from")
message_to = models.ForeignKey(User,related_name="%(class)s_to")
message=models.CharField(max_length=140,help_text="Your message")
created_on = models.DateTimeField(auto_now_add=True)
class Meta:
db_table = 'messages'
Query:messages = Messages.objects.filter(message_to = user).order_by('-created_on')[0]
Output:
message_from | message_to | message | created_on
------------------|-----------------|--------------------|--------------------
Stephen | Anto | Hi, How are you? | 2012-10-09 14:27:48
Ans: Assume Bellow model for storing messages with timelines
class Message(models.Model):
from = models.ForeignKey(User,related_name = "%(class)s_from")
to = models.ForeignKey(User, related_name = "%(class)s_to")
msg = models.CharField(max_length=255)
rating = models.IntegerField(blank='True',default=0)
created_on = models.DateTimeField(auto_now_add=True)
updated_on = models.DateTimeField(auto_now=True)
Filter messages with specified Date and Time
today = date.today().strftime('%Y-%m-%d')
yesterday = date.today() - timedelta(days=1)
yesterday = yesterday.strftime('%Y-%m-%d')
this_month = date.today().strftime('%m')
last_month = date.today() - timedelta(days=32)
last_month = last_month.strftime('%m')
this_year = date.today().strftime('%Y')
last_year = date.today() - timedelta(days=367)
last_year = last_year.strftime('%Y')
today_msgs = Message.objects.filter(created_on__gte=today).count()
yesterday_msgs = Message.objects.filter(created_on__gte=yesterday).count()
this_month_msgs = Message.objects.filter(created_on__month=this_month,created_on__year=this_year).count()
last_month_msgs = Message.objects.filter(created_on__month=last_month,created_on__year=this_year).count()
this_year_msgs = Message.objects.filter(created_on__year=this_year).count()
last_year_msgs = Message.objects.filter(created_on__year=last_year).count()
Ans: Django is named after Django Reinhardt, a gypsy jazz guitarist from the 1930s to early 1950s who is known as one of the best guitarists of all time.
Ans: Django follows Model-View Controller (MVC) architectural pattern.
Ans: Django is a high level Python's web framework which was designed for rapid development and clean realistic design.
Ans: Django is pronounced JANG-oh. Here D is silent.
Ans: Django can be broken into many components:
Models.py file: This file defines your data model by extending your single line of code into full database tables and add a pre-built administration section to manage content.
Urls.py file: It uses regular expression to capture URL patterns for processing.
Views.py file: It is the main part of Django. The actual processing happens in view.
When a visitor lands on Django page, first Django checks the URLs pattern you have created and uses information to retrieve the view. After that view processes the request, querying your database if necessary, and passes the requested information to template.
After that the template renders the data in a layout you have created and displays the page.
Ans: Django web framework is managed and maintained by an independent and non-profit organization named Django Software Foundation (DSF).
Ans: Yes, Django is quite stable. Many companies like Disqus, Instagram, Pinterest, and Mozilla have been using Django for many years.
Ans: Features available in Django web framework are:
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Ans: To start a project in Django, use the command $django-admin.py and then use the following command:
Project
_init_.py
manage.py
settings.py
urls.py
Ans: There are three possible inheritance styles in Django:
1) Abstract base classes: This style is used when you only want parent's class to hold information that you don't want to type out for each child model.
2) Multi-table Inheritance: This style is used if you are sub-classing an existing model and need each model to have its own database table.
3) Proxy models: This style is used, if you only want to modify the Python level behavior of the model, without changing the model's fields.
Ans: To set up a database in Django, you can use the command edit mysite/setting.py , it is a normal python module with module level representing Django settings.
By default, Django uses SQLite database. It is easy for Django users because it doesn't require any other type of installation. In the case of other database you have to the following keys in the DATABASE 'default' item to match your database connection settings.
Engines: you can change database by using 'django.db.backends.sqlite3' , 'django.db.backeneds.mysql', 'django.db.backends.postgresql_psycopg2', 'django.db.backends.oracle' and so on
Name: The name of your database. In the case if you are using SQLite as your database, in that case database will be a file on your computer, Name should be a full absolute path, including file name of that file.
Note: You have to add setting likes setting like Password, Host, User, etc. in your database, if you are not choosing SQLite as your database.
Ans: A template is a simple text file. It can create any text-based format like XML, CSV, HTML, etc. A template contains variables that get replaced with values when the template is evaluated and tags (%tag%) that controls the logic of the template.
Ans: No, Django is not a CMS. Instead, it is a Web framework and a programming tool that makes you able to build websites.
Ans: The session framework facilitates you to store and retrieve arbitrary data on a per-site visitor basis. It stores data on the server side and abstracts the receiving and sending of cookies. Session can be implemented through a piece of middleware.
Ans: There are three main things required to set up static files in Django:
1) Set STATIC_ROOT in settings.py
2) run manage.py collectsatic
3) set up a Static Files entry on the PythonAnywhere web tab
Ans:You have to set the SESSION_ENGINE settings to "django.contrib.sessions.backends.file" to use file based session.
Ans: Some usage of middlewares in Django is:
Ans: The Django field class types specify:
Ans: Django-admin.py: It is a Django's command line utility for administrative tasks.
Manage.py: It is an automatically created file in each Django project. It is a thin wrapper around the Django-admin.py. It has the following usage:
Ans: Signals are pieces of code which contain information about what is happening. Dispatcher is used to send the signals and listen for those signals.
Ans: Two important parameters in signals are:
Ans: The command line "Django-admin.py loaddata" is used to load data into Django. The command line will searches the data and loads the contents of the named fixtures into the database.
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