Django Tutorial 3

Posted by Derek Banas on Nov 5, 2016 in Web Design | 0 comments

In this part of my Django tutorial series we’ll learn about the built in Administration part of Django, Templates, Form Processing, Databases, Namespaces, Passing Data in URLs, and multiple useful Django functions.

If you didn’t see the previous video, you must because this is a multipart video. Here is a Django installation video. All of the code and a transcript of the video follows below.

If you find videos like this valuable consider donating a $1 on Patreon.

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Code & Transcript

You need all of the code from the previous video plus this.

# ---------- /polls/admin.py ----------

# 1 Django automates the interface used to add, change
# and delete content
# To create a user : python3 manage.py createsuperuser
# Username: admin
# Email address: db@compuserve.com
# Enter passwords

# 1 Run the server : python3 manage.py runserver
# Open localhost:8000/admin

# 1 Tell admin that our poll system has an admin interface
# in polls/admin.py

# 1 You can change any of the options and click History
# to see a list of the changes
# You can also add or delete questions

# 1 Now add more views in polls/views.py

from django.contrib import admin

# Register your models here.

# - Import Question
from .models import Question

# - Register Question for showing in admin
admin.site.register(Question)

# ---------- /polls/views.py ----------

from django.http import HttpResponse

# 7 Opens a 404 page if get doesn't supply a result
from django.shortcuts import get_object_or_404

# 2 Each view is represented by a function
# We'll create :
# index : Display the latest questions
# detail : Display the question and the choices
# results : Display question results

# - Original index function
'''
def index(request):
    return HttpResponse("You're in the polls index")
'''

# 4
# Import Question and Choice from our models file
from .models import Question, Choice

'''
# 4 New index function
def index(request):

    # 4 Receive a list of 5 questions ordered by date
    latest_question_list = Question.objects.order_by('-pub_date')[:5]

    # 4 Cycle through the questions to create a list
    output = ', '.join([q.question_text for q in latest_question_list])

    # Return the text to display
    return HttpResponse(output)

'''

# 4 This isn't the best solution because the results are
# hard coded into the Python. Let's use a template to
# separate the design from the code
# Create a directory named templates in polls
# Create a directory named polls in the templates directory
# Create a file named index.html in that polls directory
# and create the template

# 6 Create a new index function that sends the question list
# to the template

# 6 Renders a page when it is passed a template and
# any data required by the template
from django.shortcuts import render

def index(request):
    latest_question_list = Question.objects.order_by('-pub_date')[:5]

    # 6 Define the name for the data to pass to the template
    context = {
        'latest_question_list': latest_question_list,
    }

    # 6 Render the page in the browser using the template
    # and data required by the template
    return render(request, 'polls/index.html', context)


# 2 add these 3 new views

'''
def detail(request, question_id):
    return HttpResponse("You're looking at question %s" % question_id)
'''

'''
def results(request, question_id):
        response = "You're looking at the results of question %s"
        return HttpResponse(response % question_id)
'''

# 10 Let's update results() to show voting results
def results(request, question_id):

    # 10 Get the question id passed or 404
    question = get_object_or_404(Question, pk=question_id)

    # 10 Render the template
    return render(request, 'polls/results.html',
                  {'question': question})

# 10 Now create /templates/polls/results.html template

'''
def vote(request, question_id):
    return HttpResponse("You're voting on question %s" % question_id)

# 7 Let's update detail to use a 404 page and template
'''

# 9 Now we will update vote() to except the choice picked

# 9 Used to avoid receiving data twice from a form if the user
# clicks the back button
from django.http import HttpResponseRedirect

# 9 Used to return a url we can point to based on the
# current question we are dealing with
from django.urls import reverse

def vote(request, question_id):
    question = get_object_or_404(Question, pk=question_id)

    # 9 Try to get the selected radio button
    try:
        selected_choice = question.choice_set.get(pk=request.POST['choice'])

    except(KeyError, Choice.DoesNotExist):

        # 9 Re-render the form
        return render(request, 'polls/detail.html', {
            'question': question,
            'error_message': "You didn't select a choice"
        })
    else:

        # 9 If a choice was selected increment it in the DB
        selected_choice.votes += 1
        selected_choice.save()

        # 9 Protect from data being sent twice if user clicks back
        return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))


def detail(request, question_id):
    # 7 Check if the page exists, or display 404 page
    question = get_object_or_404(Question, pk=question_id)

    return render(request, 'polls/detail.html', {'question': question})

# 7 Now create the detail.html template in templates/polls/

# 2 Add them to polls/urls.py


# ---------- /polls/urls.py ----------

from django.conf.urls import url

from . import views

# 3 Add a namespace so Django knows what directory to load
# if another app has views with the same name
app_name = 'polls'

urlpatterns = [
    url(r'^$', views.index, name='index'),
    # 3 Add the 3 views
    # The data surrounded by parentheses is sent to the function
    # ?P<question_id> defines the name for the data within
    # the parentheses
    # [0-9]+ says we will match 1 or more numbers
    url(r'^(?P<question_id>[0-9]+)/$', 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'),
]

# 3 Now let's update polls/views.py

# ---------- /polls/templates/polls/index.html ----------

<!-- 5 If a list of questions is available create
an unordered list of the questions or print
that none are available -->
{% if latest_question_list %}
    <ul>
        {% for question in latest_question_list %}
            <li>
                <!-- 5 url defines directory to open based
                 on using the namespace defined in polls/urls.py
                 and the url defined in sampsite/urls.py -->
                <a href="{% url 'polls:detail' question.id %}">{{question.question_text}}</a>
            </li>
        {% endfor %}
    </ul>
{% else %}
    <p>No polls are available</p>
{% endif %}

<!-- 5 Back to polls/views.py to update index -->

# ---------- /polls/templates/polls/detail.html ----------

<!-- 8 Display the question passed and the choices
available -->

<h1>{{question.question_text}}</h1>

<!-- 8 Display error message -->
{% if error_message %}
<p><strong>{{error_message}}</strong></p>
{% endif %}

<!-- 8 Create a form which allows users to pick a choice -->
<!-- Point at the vote function in polls/views.py using
the namespace and pass the question id -->
<form action="{% url 'polls:vote' question.id %}" method="post">

<!-- 8 Protects your site from Cross Site Request Forgeries
which occur when another site tries to target your form -->
{% csrf_token %}

<!-- 8 Cycle through all choices for this question and
create a radio button for each -->
{% for choice in question.choice_set.all %}

    <!-- 8 When submitted the choice id is sent -->
    <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>

<!-- 8 Now update the vote function in polls/views.py -->

# ---------- /polls/templates/polls/results.html ----------

<!-- 11 Displays choice results for the passed question -->

<h1>{{question.question_text}}</h1>

<!-- Cycle through all the choices for the question -->
<ul>
    {% for choice in question.choice_set.all %}
        <li>
            <!-- Add a s to vote if not 1 -->
            {{choice.choice_text}} -- {{choice.votes}} vote{{choice.votes|pluralize}}
        </li>
    {% endfor %}
</ul>

<a href="{% url 'polls:detail' question.id %}">Vote Again</a>

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# ---------- /polls/admin.py ----------

# 1 Django automates the interface used to add, change

# and delete content

# To create a user : python3 manage.py createsuperuser

# Username: admin

# Email address: db@compuserve.com

# Enter passwords

# 1 Run the server : python3 manage.py runserver

# Open localhost:8000/admin

# 1 Tell admin that our poll system has an admin interface

# in polls/admin.py

# 1 You can change any of the options and click History

# to see a list of the changes

# You can also add or delete questions

# 1 Now add more views in polls/views.py

from django.contrib import admin

# Register your models here.

# - Import Question

from .models import Question

# - Register Question for showing in admin

admin.site.register(Question)

# ---------- /polls/views.py ----------

from django.http import HttpResponse

# 7 Opens a 404 page if get doesn't supply a result

from django.shortcuts import get_object_or_404

# 2 Each view is represented by a function

# We'll create :

# index : Display the latest questions

# detail : Display the question and the choices

# results : Display question results

# - Original index function

'''

def index(request):

return HttpResponse("You're in the polls index")

'''

# 4

# Import Question and Choice from our models file

from .models import Question, Choice

'''

# 4 New index function

def index(request):

# 4 Receive a list of 5 questions ordered by date

latest_question_list = Question.objects.order_by('-pub_date')[:5]

# 4 Cycle through the questions to create a list

output = ', '.join([q.question_text for q in latest_question_list])

# Return the text to display

return HttpResponse(output)

'''

# 4 This isn't the best solution because the results are

# hard coded into the Python. Let's use a template to

# separate the design from the code

# Create a directory named templates in polls

# Create a directory named polls in the templates directory

# Create a file named index.html in that polls directory

# and create the template

# 6 Create a new index function that sends the question list

# to the template

# 6 Renders a page when it is passed a template and

# any data required by the template

from django.shortcuts import render

def index(request):

latest_question_list = Question.objects.order_by('-pub_date')[:5]

# 6 Define the name for the data to pass to the template

context = {

'latest_question_list': latest_question_list,

}

# 6 Render the page in the browser using the template

# and data required by the template

return render(request, 'polls/index.html', context)

# 2 add these 3 new views

'''

def detail(request, question_id):

return HttpResponse("You're looking at question %s" % question_id)

'''

def results(request, question_id):

response = "You're looking at the results of question %s"

return HttpResponse(response % question_id)

'''

# 10 Let's update results() to show voting results

def results(request, question_id):

# 10 Get the question id passed or 404

question = get_object_or_404(Question, pk=question_id)

# 10 Render the template

return render(request, 'polls/results.html',

{'question': question})

# 10 Now create /templates/polls/results.html template

'''

def vote(request, question_id):

return HttpResponse("You're voting on question %s" % question_id)

# 7 Let's update detail to use a 404 page and template

'''

# 9 Now we will update vote() to except the choice picked

# 9 Used to avoid receiving data twice from a form if the user

# clicks the back button

from django.http import HttpResponseRedirect

# 9 Used to return a url we can point to based on the

# current question we are dealing with

from django.urls import reverse

def vote(request, question_id):

question = get_object_or_404(Question, pk=question_id)

# 9 Try to get the selected radio button

try:

selected_choice = question.choice_set.get(pk=request.POST['choice'])

except(KeyError, Choice.DoesNotExist):

# 9 Re-render the form

return render(request, 'polls/detail.html', {

'question': question,

'error_message': "You didn't select a choice"

})

else:

# 9 If a choice was selected increment it in the DB

selected_choice.votes += 1

selected_choice.save()

# 9 Protect from data being sent twice if user clicks back

return HttpResponseRedirect(reverse('polls:results', args=(question.id,)))

def detail(request, question_id):

# 7 Check if the page exists, or display 404 page

question = get_object_or_404(Question, pk=question_id)

return render(request, 'polls/detail.html', {'question': question})

# 7 Now create the detail.html template in templates/polls/

# 2 Add them to polls/urls.py

# ---------- /polls/urls.py ----------

from django.conf.urls import url

from . import views

# 3 Add a namespace so Django knows what directory to load

# if another app has views with the same name

app_name = 'polls'

urlpatterns = [

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

# 3 Add the 3 views

# The data surrounded by parentheses is sent to the function

# ?P<question_id> defines the name for the data within

# the parentheses

# [0-9]+ says we will match 1 or more numbers

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'),

]

# 3 Now let's update polls/views.py

# ---------- /polls/templates/polls/index.html ----------

<!-- 5 If a list of questions is available create

an unordered list of the questions or print

that none are available -->

{% if latest_question_list %}

<ul>

{% for question in latest_question_list %}

<li>

<!-- 5 url defines directory to open based

on using the namespace defined in polls/urls.py

and the url defined in sampsite/urls.py -->

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

</li>

{% endfor %}

</ul>

{% else %}

<p>No polls are available</p>

{% endif %}

# ---------- /polls/templates/polls/detail.html ----------

<!-- 8 Display the question passed and the choices

available -->

<h1>{{question.question_text}}</h1>

{% if error_message %}

<p><strong>{{error_message}}</strong></p>

{% endif %}

<!-- Point at the vote function in polls/views.py using

the namespace and pass the question id -->

<!-- 8 Protects your site from Cross Site Request Forgeries

which occur when another site tries to target your form -->

{% csrf_token %}

<!-- 8 Cycle through all choices for this question and

create a radio button for each -->

{% 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 %}

</form>

# ---------- /polls/templates/polls/results.html ----------

<h1>{{question.question_text}}</h1>

<ul>

{% for choice in question.choice_set.all %}

<li>

{{choice.choice_text}} -- {{choice.votes}} vote{{choice.votes|pluralize}}

</li>

{% endfor %}

</ul>

<a href="{% url 'polls:detail' question.id %}">Vote Again</a>

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Django Tutorial 3

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