Getting started

Hello world

The following small code shows you how to print “hello world” using Plastic web framework:

from plastic.app import BaseApp

App = BaseApp.clone()

@App.route('/')
def hello(request):
    return 'Hello, world!'

if __name__ == '__main__':
    App().run()

Save the script (say it’s hello.py) and execute it:

$ python hello.py
 * Running on http://127.0.0.1:5555/
 * Restarting with reloader

Then open http://127.0.0.1:5555/ in your favorite web browser. The page says you “Hello, world!”:

How it was going on?

In the above example, we created our application class named App:

App = BaseApp.clone()

Yes, it’s a class and also a subtype of plastic.app.BaseApp. It can do several things e.g. routing, service. Indeed it’s a shorthand of the following “ordinary” inheritance code:

class App(BaseApp):
    pass

And then we defined a web page named hello():

@App.route('/')
def hello(request):
    return 'Hello, world!'

We call these functions view functions (as like in Django or Flask). View functions can be routed using BaseApp.route() decorator, which is a convenient form of BaseApp.add_rule() method:

from werkzerug.routing import Rule

def hello(request):
    return 'Hello, world'
App.add_rule(Rule('/'), hello)

A view function has to take an argument at least, for getting a request. In a request object there are many information about a request e.g. HTTP method, HTTP headers, WSGI environment values.

It has to return a response. If it’s simply a string, it will be a content of a response that Content-Type is text/plain. It also can return an instance of plastic.message.Response.

Lastly, the following line makes an app to be served:

if __name__ == '__main__':
    App().run()

The first if statement is a common idiom of Python to determine whether the file is directly executed by python as a script or imported by other module or script as a module. If it’s imported by others as hello module, the code in the if statement will be ignored. If it’s exeucted by python as a script (e.g. python hello.py), the code below will be also executed.

The run() method serves the app, so the above two lines mean: “run the web server if the file isn’t imported by others but executed as a script.” It’s not a class method but an instance method, so it should be instantiated first: App().