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Python Web Application using Table Storage

In this tutorial, you will learn how to create an application that uses Table Storage with the Windows Azure Client Libraries for Python. If this is your first Python Azure app, you may wish to take a look at Django Hello World Web Application first.

For this guide, you will create a web-based task-list application that you can deploy to Windows Azure. The task list allows a user to retrieve tasks, add new tasks, and mark tasks as completed. We'll be using Django as the web framework.

The task items are stored in Windows Azure Storage. Windows Azure Storage provides unstructured data storage that is fault-tolerant and highly available. Windows Azure Storage includes several data structures where you can store and access data, and you can leverage the storage services from the APIs included in the Windows Azure SDK for Python or via REST APIs. For more information, see Storing and Accessing Data in Windows Azure.

You will learn:

How to work with Windows Azure Table Storage service

A screenshot of the completed application will be similar as below (the added tasks items will be different):

Note

To complete this tutorial, you need a Windows Azure account. You can create a free trial account and enable preview features in just a couple of minutes. For details, see Windows Azure Free Trial.

Setting Up the Development Environment

Note: If you need to install Python or the Client Libraries, please see the Python Installation Guide.

Note for Windows: if you used the Windows WebPI installer, you already have Django and the Client Libs installed.

Create A Storage Account In Windows Azure

To use storage operations, you need a Windows Azure storage account. You can create a storage account by following these steps. (You can also create a storage account using the REST API.)

Log into the Windows Azure Management Portal.
At the bottom of the navigation pane, click NEW.
Click DATA SERVICES, then STORAGE, and then click QUICK CREATE.
In URL, type a subdomain name to use in the URI for the storage account. The entry can contain from 3-24 lowercase letters and numbers. This value becomes the host name within the URI that is used to address Blob, Queue, or Table resources for the subscription.
Choose a Region/Affinity Group in which to locate the storage. If you will be using storage from your Windows Azure application, select the same region where you will deploy your application.
Optionally, you can enable geo-replication.
Click CREATE STORAGE ACCOUNT.

Create A Django Project

Here are the steps for creating the app:

Create a default Django Project named 'TableserviceSample'
From the command line, cd into a directory where you’d like to store your code, then run the following command:
```
django-admin.py startproject TableserviceSample
```
Add a new Python file views.py to the project

Add the following code to views.py to import the required Django support:

from django.http import HttpResponse
from django.template.loader import render_to_string
from django.template import Context

Create a new folder named templates under the TableserviceSample/TableserviceSample folder.
Edit the application settings so your templates can be located. Open settings.py and add the following entry to INSTALLED_APPS:
```
'TableserviceSample',
```
Add a new Django template file mytasks.html to the templates folder and add following code to it:

<html>
    <head><title></title></head>
    <body>
    <h2>My Tasks</h2> <br>
    <table border="1"> 
    <tr>
    <td>Name</td><td>Category</td><td>Date</td><td>Complete</td><td>Action</td></tr>
    {% for entity in entities %}
    <form action="update_task" method="GET">
    <tr><td>{{entity.name}} <input type="hidden" name='name' value="{{entity.name}}"></td>
    <td>{{entity.category}} <input type="hidden" name='category' value="{{entity.category}}"></td>
    <td>{{entity.date}} <input type="hidden" name='date' value="{{entity.date}}"></td>
    <td>{{entity.complete}} <input type="hidden" name='complete' value="{{entity.complete}}"></td>

    <td><input type="submit" value="Complete"></td>
    </tr>
    </form>
    {% endfor %}
    </table>
    <br>
    <hr>
    <table border="1">
    <form action="add_task" method="GET">
    <tr><td>Name:</td><td><input type="text" name="name"></input></td></tr>
    <tr><td>Category:</td><td><input type="text" name="category"></input></td></tr>
    <tr><td>Item Date:</td><td><input type="text" name="date"></input></td></tr>
    <tr><td><input type="submit" value="add task"></input></td></tr>
    </form>
    </table>
    </body>
    </html>

Import windowsazure storage module

Add following code on the top of views.py just after Django imports

from azure.storage import TableService

Get storage account name and account key

Add the following code to views.py just after the windowsazure import, and replace 'youraccount' and 'yourkey' with your real account name and key. You can get an account name and key from azure management portal.

account_name = 'youraccount'
account_key = 'yourkey'

Create TableService

Add following code after “account_name …”

table_service = TableService(account_name=account_name, account_key=account_key)
table_service.create_table('mytasks')

List tasks

Add function list_tasks to views.py:

def list_tasks(request): 
    entities = table_service.query_entities('mytasks', '', 'name,category,date,complete')    
    html = render_to_string('mytasks.html', Context({'entities':entities}))
    return HttpResponse(html)

Add task

Add the function add_task to views.py:

def add_task(request):
    name = request.GET['name']
    category = request.GET['category']
    date = request.GET['date']
    table_service.insert_entity('mytasks', {'PartitionKey':name+category, 'RowKey':date, 'name':name, 'category':category, 'date':date, 'complete':'No'}) 
    entities = table_service.query_entities('mytasks', '', 'name,category,date,complete')
    html = render_to_string('mytasks.html', Context({'entities':entities}))
    return HttpResponse(html)

Update task status

Add the function update_task to views.py:

def update_task(request):
    name = request.GET['name']
    category = request.GET['category']
    date = request.GET['date']
    partition_key = name + category
    row_key = date
    table_service.update_entity('mytasks', partition_key, row_key, {'PartitionKey':partition_key, 'RowKey':row_key, 'name': name, 'category':category, 'date':date, 'complete':'Yes'})
    entities = table_service.query_entities('mytasks', '', 'name,category,date,complete')    
    html = render_to_string('mytasks.html', Context({'entities':entities}))
    return HttpResponse(html)

Mapping urls

Now you need to map the URLs in the Django app. Open urls.py and add following mappings to urlpatterns:

url(r'^$', 'TableserviceSample.views.list_tasks'),
url(r'^list_tasks$', 'TableserviceSample.views.list_tasks'),
url(r'^add_task$', 'TableserviceSample.views.add_task'),
url(r'^update_task$', 'TableserviceSample.views.update_task'),

Run the application

Switch to the "TableserviceSample" directory, if you haven't already, and run the command:

python manage.py runserver
Point your browser to: http://127.0.0.1:8000/. Replace 8000 with the real port #

You can now click "Add Task" to create one and then click the "Complete" button to update the task and set its status to Yes.

Running the Application in the Compute Emulator, Publishing and Stopping/Deleting your Application

Now that you've successfully run your app on the built-in Django server, you can test it out further by deploying it to the Windows Azure emulator (Windows only) and then publishing to Windows Azure. For general instructions on how to do this, please refer to the article "Django Hello World Web Application" which discusses these steps in detail.

Next Steps

Now that you’ve learned the basics of the Windows Azure Table storage service, follow these links to learn how to do more complex storage tasks.

See the MSDN Reference: Storing and Accessing Data in Windows Azure
Visit the Windows Azure Storage Team Blog: http://blogs.msdn.com/b/windowsazurestorage/