Django Best Practices

Sudip Kafle

@kaflesudip

A web framework for perfectionists with deadline

Why Django?

Fast

Batteries included

Secure

Community

We ♥ Python

I am a beginner

Learn Python - http://www.diveintopython3.net/

Try Django's official Tutorial - https://docs.djangoproject.com/en/1.7/intro/tutorial01/

Learn Test Driven Development  http://chimera.labs.oreilly.com/books/1234000000754

Learn about Django's best Practices  http://www.amazon.com/Two-Scoops-Django-Best-Practices/dp/098146730X

MVC MTV Architecture

Models -> Models

Views -> Templates

Controller -> Entire Framework

Browser

Views

Models

Templates

URLs

http://flipkarma.com/project/corporate-decision-support-system-for-telecommunic/

'^project/(?P<slug>[-\w]+)/$'

class ProjectDetailView(DetailView):

class Project(models.Model):

select * from Project where slug='...'

Raw Data

Data(objects)

Data + other..

HTML

URLS

Maps regular expressions to Python functions.

'/project/[0-9]+'

why not '^project/{id}/$'

Never do '/project/(.+)'

Models

# product/models.py


class Product(models.Model):
    name = models.Charfield()
    description = models.StringField()
    price = models.FloatField()
    category = models.ForeignKeyField(subject)

    def get_cheapest(self):
        .........................



+---------------------+--------------+------
| Field               | Type         | Key |
+---------------------+--------------+-----|
| id                  | int(11)      | PRI |
| name                | varchar(300) |     |
| description         | longtext     |     |
| price               | float        |     |
| category_id         | int(11)      | MUL |
+---------------------+--------------+-----+

Most of the business Logic reside in models

Views

Gets the data from models and sends it to the templates

No business logic

from .models import Product

def product(request, id):
    product_object = Product.objects.get(id=id)
    return render_to_response("products.html", {"product": product_object})

Templates

HTML + some templating languages.

<!-- product.html -->

<!DOCTYPE html>
<html lang="en">
.............
<body>

  <h1>{{product.name}}</h1>

  {% if product.description %}
    {{ product.description }}
  {% endif %}
  
</body>
</html>

<!-- product.html -->

<!DOCTYPE html>
<html lang="en">
.............
<body>

  <h1>Nike Shoes</h1>

  The shoes are really awesome
  priced at ...
  
</body>
</html>




# at models
def price_in_dollar(self, conversion_rate):
    return (self.price) / conversion_rate


# at views
price_in_dollar = product.price_in_dollar(101)


# at templates
Price in $: {{price_in_dollar}}

```
Fat models
```
```
Thin views
```
```
Dumb templates
```

Apps


|   |   -- project
|   |       |-- app1
|   |       |   |-- __init__.py
|   |       |   |-- admin.py
|   |       |   |-- forms.py
|   |       |   |-- models.py
|   |       |   |-- tests.py
|   |       |   `-- urls.py
|   |       |-- app2
|   |       |   |-- __init__.py
|   |       |   |-- admin.py
|   |       |   |-- forms.py
|   |       |   |-- models.py
|   |       |   `-- urls.py
|   |       |-- project
|   |       |   |-- __init__.py
|   |       |   |-- settings.py
|   |       |   |-- urls.py
|   |       |   `-- wsgi.py
|   |       |-- manage.py
|   |       |-- static
|   |       |-- templates

Golden Rule for App Design

Design app that does one thing

Try to explain what your app does in One sentence
If you have 'and' in the sentence,
Break it into two or more apps
My app provides the ability to manage user accounts and upload videos.

Mistakes as Beginners

Don't mess up with settings.py

Don't change STATIC settings. The defaults work on development environment without collectstatic.
TEMPLATE_DIR, DATABASES and INSTALLED_APPS are to be changed.
Windows style back slash - 'project\app\..'
Use - 'project/app/...

Don't be afraid to create multiple apps

One App for the complete project will make it painful later

Leverage the power of forms.py

Don't hardcode the urls

Bad:

Good:

Prefer reverse in views.

reverse('product_page', args=(id,))

Don't mess up with security

Avoid csrf_exempt in most cases
Avoid {{ | safe }} filter in templates
Don't trust user's data.

Final Tips

```
Use Virtualenv
```
```
Use Class Based Views
```
```
Django Debug Toolbar
```
```
iPython / bPython
```
```
API's - Django Rest Framework
```
```
Don't ignore tests.
```

Use Fabric, Ansible or chef for deployment

```
Master Python, data structures ...
```

Twitter / fb/ linkedin/ G+: @kaflesudip

meroanswer.com

Sudip Kafle

flipkarma.com

sudip@phunka.com

CTO and CoFounder at Phunka Technogies