Developing Software As A Service App with Python & Django

Developing Software As A
Service with Python &
Django
Allan Spartacus Mangune, CPA, MsCIS

Friday, January 18, 13

Allan Spartacus Mangune
Certiﬁed Public Accountant
MSCIS - University of Phoenix
Certiﬁed Scrum Master
Certifed Ethical Hacker
Microsoft MVP for ASP.NET
6 years in public accounting
13 years in software development and consulting


Taughtworks, Inc.

Microsoft Certiﬁed Partner for Learning Solutions
2/F Liberty Plaza Building, H. V. Dela Costa Street,
Makati City


Our New Ofﬁce

5/F 6784 Ayala Avenue corner V.A. Ruﬁno Street, Makati City


Agenda
Software As A Service For Small Businesses
Procurement and Inventory Management
Sales Order and Invoicing Management
Customer Relationship Management
Technologies
Python, Django, Memcache, & Postgresql
Deployment and Maintenance


Primogul

Customer
Procurement Inventory Sales Order Sales Invoice
Relation

Cost Revenue
200
150
100
50
2007 2008 0
2009 2010
Reports and Analytics Engines


Procurement

Maintain information about vendors
Use purchase orders to order inventory items
Manage receipts of goods
Manage billings from vendors


Inventory

Manage inventory information, location and movements
Physical inventory count
Inventory worksheets
Inventory adjustments
Inventory valuation


Sales Order

Create quotations for customers
Convert quotations to sales invoice or order
Create sales orders
Allocate inventory items to sales orders


Sales Invoice

Invoice customers for delivered goods or services


Software As A Service

Software on-demand
Multi-tenant environment
Pricing is based on number of seats and usage
parameters


Technologies

Python
Django
Postgresql
Memcache


Python 101


Python

Powerful and easy to learn programming language
Requires an interpreter to run
Python interpreter and libraries can be downloaded
from python.org
Runs on Mac OS X, Unix, and Windows


Invoking the Interpreter
Allan-Spartacus-Mangunes-MacBook-Pro:~ allan$ python
Python 2.7.2 (default, Jun 20 2012, 16:23:33)
[GCC 4.2.1 Compatible Apple Clang 4.0 (tags/Apple/clang-418.0.60)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>>


Variables

The equal (‘=’) sign is used to assign a value
length = 40
A value can be assigned to several variables
a=b=c=d=6
A variable must be assigned with a value prior to using
it


Lists
Expressed a list of values separated by a comma
Placed between square brackets [ ]
Can be of different types
x = [‘hello’, ‘world’, 101, 88]
Indices begins at 0
x[0] equals ‘hello’
x[3] equals 88


Control Flow

while statement
if statement
for statement


while Statement
while loop executes while the condition is true
while {condition}:
{run the code}
{have it indented}
Example
>>> x, y = 0, 1
>>> while y < 12:
... print y
... x, y = y, x+y
...
1
1
2
3
5
8

if Statement
If the condition is true, the code block is executed
if {condition}:
{run the code}
{have it indented}
Example
>>> a = int(raw_input('Please enter a number: ')) >>> a = int(raw_input('Please enter a number: '))
Please enter a number: 24 Please enter a number: 0
>>> if a < 0: >>> if a < 0:
... print "You entered a number lower than zero" ... print "You entered a number lower than zero"
... else: ... elif a == 0:
... print "You entered a number greater than zero" ... print "You entered a number zero"
... ... else:
You entered a number greater than zero ... print "You entered a number greater than zero"
...
You entered a number zero


for Statement
Iterates over the items
for {i in list}:
{run the code}
{have it indented}
Example
>>> list = ['dog', 'cat', 'mouse']
>>> for i in list:
... print i, len(i)
...
dog 3
cat 3
mouse 5


Functions
Deﬁne
def foo(arguments):
{run the code}
{have it indented}
Example
>>> def foo(num):
... x, y = 0, 1
... while y < num:
... print y
... x, y = y, x+y
...
>>> foo(20)
1
1
2
3
5

Classes
Blueprint of an object
Provide the fundamental features of Object-Oriented
Programming
Can inherit from multiple base classes
An instance can be modiﬁed during runtime
Data members and member methods are public.
Member methods are virtual
Conventions tells us that member that begins with an
underscore ‘_’ shall be treated as private

Class Deﬁnition/Instance
Simplest form:
class Foo:
<statement_1>
.
.
.
<statement_2>

Statements inside a class are usually method
deﬁnitions
class Foo:
def bar(num):
x, y = 0, 1
while y < num:
print y
x, y = y, x+y


Django 101


Django

“Web framework for for perfectionists with deadlines” -
djangoproject.com
High-level Python Web framework


Django Framework

Object-relational mapper - Deﬁne data models entirely
in Python
Automatic admin interface - Production-ready user
interface to add/update contents
Elegant URL design - cruft-free URL
Template system - Extensible template language
Cache system - Hooked into memcache
Internalization - Multi-language support Source: djangoproject.com


Sites that Use Django

Disqus
Instagram
Mozilla
OpenStack
Pinterest
PolitiFact.com
Rdio
Source: djangoproject.com


Installing Django
Requires Python
python.org
Usually installed on Mac OS X, Other Unix system
You may need to set up your database engine like
Postgresql, Mysql or Oracle
Install a version for speciﬁc operating system
Get the ofﬁcial release
Latest version is 1.4.3
python > import django

Creating Django app
Auto-generate the code to establish the project
Create a project directory
django-admin.py startproject blog

Project structure
demo/
manage.py
blog/
__init__.py
settings.py
urls.py
wsgi.py


Django Development Server
Lightweight web server written in Python
You can use this during development
Allan-Spartacus-Mangunes-MacBook-Pro:blog allan$ python manage.py runserver
Validating models...

0 errors found
Django version 1.4.1, using settings 'blog.settings'
Development server is running at http://127.0.0.1:8000/

Don’t use this server in the production


Setting up Database
Edit the blog/settings.py
Python module that contains Django settings
Change the keys in the DATABASES
DATABASES = {
'default': {
'ENGINE': 'django.db.backends.sqlite3', # Add 'postgresql_psycopg2', 'mysql', 'sqlite3' or
'oracle'.
'NAME': '/Users/allan/demo/blog/blog.db', # Or path to database file if using sqlite3.
'USER': '', # Not used with sqlite3.
'PASSWORD': '', # Not used with sqlite3.
'HOST': '', # Set to empty string for localhost. Not used with sqlite3.
'PORT': '', # Set to empty string for default. Not used with sqlite3.


INSTALLED_APPS
Holds the names of activated applications
INSTALLED_APPS = (
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.sites',
'django.contrib.messages',
'django.contrib.staticfiles',
)

Each app holds one database table
Allan-Spartacus-Mangunes-MacBook-Pro:blog allan$ python manage.py syncdb
Creating tables ...
Creating table auth_permission
Creating table auth_group_permissions
Creating table auth_group
Creating table auth_user_user_permissions
Creating table auth_user_groups
Creating table auth_user
Creating table django_content_type
Creating table django_session
Creating table django_site


Models
Project vs App
An App is a web application that contains
functionalities
A Project is a collection of Apps
To create an App
Allan-Spartacus-Mangunes-MacBook-Pro:blog allan$ python manage.py startapp entries
Allan-Spartacus-Mangunes-MacBook-Pro:blog allan$ ls entries
__init__.py! models.py! tests.py!views.py

The entries/ directory holds the blog entries application


Models
Deﬁne models
database layouts with metadata
Edit entries/models.py
from django.db import models

class Entry(models.Model):
text = models.CharField(max_length=2000)
pub_date = models.DateTimeField('date published')

The model tells Django to create the db schema and
database-access API


Model activation
Edit the settings.py ﬁle and add ‘entries’
INSTALLED_APPS = (
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.sites',
'django.contrib.messages',
'django.contrib.staticfiles',
'entries'

)

Create the tables
Allan-Spartacus-Mangunes-MacBook-Pro:blog allan
$ python manage.py sql entries
$ python manage.py syncdb
BEGIN;
Creating tables ...
CREATE TABLE "entries_entry" (
Creating table entries_entry
"id" integer NOT NULL PRIMARY KEY,
Installing custom SQL ...
"text" varchar(2000) NOT NULL,
Installing indexes ...
"pub_date" datetime NOT NULL
Installed 0 object(s) from 0 fixture(s)
)
;
$
COMMIT;


Activating Admin Site
Not activated by default
To activate:
Uncomment ‘django.contrib.admin’ in the
INSTALLED_APPS
INSTALLED_APPS = (
'django.contrib.auth', Allan-Spartacus-Mangunes-MacBook-Pro:blog
'django.contrib.contenttypes', allan$ python manage.py syncdb
'django.contrib.sessions', Creating tables ...
'django.contrib.sites', Creating table django_admin_log
'django.contrib.messages', Installing custom SQL ...
'django.contrib.staticfiles', Installing indexes ...
'django.contrib.admin', Installed 0 object(s) from 0 fixture(s)
)

Edit the blog/urls.py
Allan-Spartacus-Mangunes-MacBook-Pro:blog
# Uncomment the next two lines to enable
allan$ python manage.py runserver
the admin:
Validating models...
from django.contrib import admin
admin.autodiscover()
0 errors found


Setting up Views
Represented by a Python function
Requires you to set up the URL in the URLconf module
ROOT_URLCONF setting
ROOT_URLCONF = 'blog.urls'

Edit blog/urls.py
urlpatterns = patterns('',
url(r'^entries/$', 'entries.views.index'),

# Uncomment the next line to enable the admin:
url(r'^admin/', include(admin.site.urls)),
)


Setting up Views
Write a view function on entries/views.py
from django.template import Context, loader
from entries.models import Entry
from django.http import HttpResponse

def index(request):
latest_entry_list = Entry.objects.all().order_by('-pub_date')[:5]
t = loader.get_template('entries/index.html')
c = Context({
'latest_entry_list': latest_entry_list
})
return HttpResponse(t.render(c))

Create a template ﬁle
{% if latest_entry_list %}
<ul>
{% for entry in latest_entry_list
TEMPLATE_DIRS = ( %}
'/Users/allan/demo/blog/templates', <li><a href="/entries/
) {{entry.id}}">{{entry.text}}</a></li>
{% endfor %}
</ul>
{% endif %}


Q and A


Allan Spartacus Mangune
allan@taughtworks.com
facebook.com/mangune


THANK YOU


Developing Software As A Service App with Python & Django

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