Brandon Rhodes - Python Web Technologies

When I met the Plone world around 2008, I saw there were lots of small companies and individual consultants. It inspired me to quit my job and university. Then the economy collapsed. Coincidence?

Movie The Social Network, 2010. When I heard about this movie, I thought it was going to be horrible. A movie about Facebook, really? But it was really good writing. One line struck me especially: "We don't even know what it is yet." Often we will get a new technology, and in retrospect have no idea what it was yet. We invent something, but we don't even know what it is yet.

The web in Python, end of the nineties. It was not much, it did not look like clean code today. The web was young. The blink tag, anyone? These two not yet mature technologies met, and mingled.

What does Python offer? What sets it apart?

• Reflection. Your program can look at itself, like in a mirror. Things like: list all functions of a class, ask the type, get an attribute by name. Not a lot of languages did that.
• Object oriented. Not just object based, allowing you to split functionality over several objects. But sub classing, multiple inheritance. You get invited to write new methods for existing classes. (And it eats a whole level of indentation, but that is another story.)
• Dynamic. You can wind up with code and objects that don't even exist in your raw source code. You can generate code on the fly, insert variables dynamically/magically. Such things might not make your code more readable though: code that does not even exist on the file system?
• Simple. Einstein: "Things should be as simple as possible, but no simpler." Dan McKinley, book Choose Boring Technology: "Every company gets about three innovation tokens." You can do about three new things without falling over. Are you going to use MongoDB? You have just used up one of your innovation tokens. Only choose new exiting technology in strategic places. For the rest: just use MySQL, Postgres, Python. Boring, but stable.

Some Python web technologies: Django, Flask, Bottle, Pyramid, Morepath. Flask and Django are an order of magnitude more popular. I created this list, found the same list somewhere else. But some techs fitting in the middle were forgotten, like web.py, web2py, CherryPy.

Flask and Django:

• Views are plain functions
• explicit registration, not reflection
• your app can start small and simple

Today, Django stands as Python's default first framework. Flask actually has more github 'stars' for people who follow it. Yet there are far more Django conferences or meetings world wide. Django gives you a good start. Years later, you may get more opinionated, with good reasons, and choose your own ORM and a different, smaller framework. As a beginner, Django just helps you a lot.

And Django has a forms library. Wait, that may involve classes. You may need inheritance and introspection. But good programmers don't avoid complexity when it helps them. Then again, a form library is a bit like backing up a truck with multiple trailers. You have knobs to control how they are going, but can you do that without failure? And you are probably missing all kinds of knobs that the forms library has not thought about. But a forms library does automatic validation, refills forms for retry, does cross site scripting, which a new web developer probably does not even think about. So it is good for them to use it.

Flask has become the go-to second framework, for when you know what you are doing.

But will we keep writing Python for the web? We have competition. Javascript is in every browser. With Node.js you even have it on the server.

Javascript is a much cleaner story from the outside. Python has 2 versus 3, C Python versus PyPy. For Javascript on the server, everyone uses Node.js, which is the PyPy of Javascript. And for ES6 there is a cross compiler to ES5.

But, you say: Python has reflection, generators, iterators, classes, modules, and Javascript has not. Wrong. ES6 adds this. You turn your back, and suddenly a language has involved. Javascript has Python features! Vi has syntax highlighting! "Everything that rises must converge." Languages grow similar.

But what about the fact that Javascript is just dumb?

40 - '30' -> 10
40 + '30' -> '4030'

In Python you get a helpful traceback when you try this, instead of running into undebuggable errors later on. Ah, but in TypeScript you get the same. They fight back successfully against the broken type system. And you can cross compile it to ES5.

So Javascript is a contender, is gaining features, and becoming safer.

There has always been another language that was more popular than Python. There is nothing new. What are Python's advantages then?

It is becoming the world's default language. Science is moving to Python. Data is moving to Python. At weather conferences there is now a Python track. Simple syntax is perfect for the occasional programmer, who has other stuff to do, like science. You do your science, and one every three weeks you write a small program. Django Girls organizes lots of weekends around the world where women use Python to write their first website. The new programmer needs Python, because it is simple.

The web and Python met when both were immature. In the years, both learned the patterns to make the web possible and sometimes even simple to program for. And even after all this years, we don't even know what it is yet.

Questions?

First language for a child? Scratch is good for young children. Python is a good language to get used to. In the US it has become the default in universities for courses.

Where at the language syntax level has Python done anything really new? When you open a file, once PyPy got popular, it got clear that files would remain open. We had to have a way to run cleanup code, even when exceptions rose. So we did try/finally, like in the Java world. It solves the problem... and it is ugly because it is Java. So we decided we needed to do one better. I believe we innovated with the with statement. It was not intuitive for me at first, but it is very helpful. It is marvellous for any kind of recursive context management, changing directories being sure that you will return to the previous directory.

In Javascript you have classes now, finally, but the Python community is far more used to it, right, which helps? Yes. Node and Javascript are still in a period of change, features have not been around for a decade. Writing in NodeJS you have spent one of your innovation tokens, writing Python you still have that one.

Find me on Twitter: @brandon_rhodes.