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Python 3 Web Development Review

Python 3 Web DevelopmentThe problem with Python 3 Web Development Beginner’s Guide, by Michel Anders, is one of expectations (disclaimer: I received a free eBook from Packt for review). Let’s start with the title… First we have Python 3 Web Development. This immediately sets the wrong expectations because:

  1. There’s almost as much jQuery & Javascript as there is Python.
  2. Most of the Python code is not Python 3 specific, and the code that is could easily be translate to Python 2.
  3. Much of the Python code either uses CherryPy or is for generating HTML. This is not immediately obvious, but becomes apparent in Chapter 3 (which is available as a free PDF download: Chapter 3 – Tasklist I Persistence).

Second, this book is also supposed to be a Beginner’s Guide, but that is definitely not the case. To really grasp what’s going on, you need to already know the basics of HTML, jQuery interaction, and how HTTP works. Chapter 1 is an excellent introduction to HTTP and web application development, but the book as a whole is not beginner material. I think that anything that uses Python metaclasses automatically becomes at least intermediate level, if not expert, and the main thrust of Chapter 7 is refactoring all your straightforward database code to use complicated metaclasses.

However, if you mentally rewrite the title to be “Web Framework Development from scratch using CherryPy and jQuery”, then you’ve got the right idea. The book steps you through web app development with CherryPy, database models with sqlite3, and plenty of HTML and jQuery for interface generation and interaction. While creating example applications, you slowly build up a re-usable framework. It’s an interesting approach, but unfortunately it gets muddied up with inline HTML rendering. I never thought a language as simple and elegant as Python could be reduced to the ugliness of common PHP, but generating HTML with string interpolation inside the same functions that are accessing the database gets pretty close. I kept expecting the author to introduce template rendering, which is a major part of most modern web development frameworks, but it never happened, despite the plethora of excellent Python templating libraries.

While reading this book, I often had the recurring thought “I’m so glad I use Django“. If your aim is rapid application development, this is not the book for you. However, if you’re interested in creating your own web development framework, or would at least like to understand how a framework like Django could be created, then buy a copy Python 3 Web Development.

Far Future Expires Header with django-storages S3Storage

One way to decrease your site’s load time is to set a far future Expires header on all your static content. This doesn’t help first-time visitors, but can greatly improve the experience of returning visitors. And you get to decrease your bandwidth needs at the same time, because all your static content will be cached by their browser.

S3

weotta puts all of its awesome plan images in Amazon’s S3 using django-storages S3Storage backend, which by default does not set any Expires header. To remedy this, I set AWS_HEADERS in settings.py like so

from datetime import date, timedelta
tenyrs = date.today() + timedelta(days=365*10)
# Expires 10 years in the future at 8PM GMT
AWS_HEADERS = {
	'Expires': tenyrs.strftime('%a, %d %b %Y 20:00:00 GMT')
}

Now every uploaded file gets an Expires header set to 10 years in the future.

upload_to

One potential drawback to using a far future Expires header is that if you change the file content without also changing the file name, no one will notice because they’ll keep using the old cached version of the file. Luckily, Django makes it easy to create (mostly) unique new file names by letting you include strftime formatting codes in a FileField or ImageField upload_to path, such as upload_to='images/%Y/%m/%d'. This way, every uploaded file automatically gets stored by date, which means it would take some deliberate effort to change the contents of a file without also changing the file name.