Pyjs Python Javascript Compiler, Desktop Widget Set and RIA Web Framework

Overview

Like GWT, Pyjs translates a Python application and
libraries (including UI widgets and DOM classes) into a
Javascript application and libraries,
and packages it all up:

1. pyjs translates Python code to Javascript by walking
   the Python abstract syntax tree and generating Javascript.
2. pyjslib takes care of Python types that require
   a custom Javascript implementation for pyjs to work. For example,
   even though Python lists are similar to Javascript arrays, Python
   lists are converted to custom objects that implement methods such
   as append.
3. UI widgets and a DOM library are provided as a
   convenience. They are written in Python and, like everything else,
   they are translated to Javascript for deployment. These are based
   on those in GWT.
4. build manages the overall translation of
   individual components and creates a set of .html
   and .js files that can be served up by a Web server.

Hello World

The omnipresent hello world example, let's call it 'Hello Pyjs':

from pyjamas.ui.RootPanel import RootPanel
from pyjamas.ui.Label import Label
l = Label('Hello Pyjs')
RootPanel().add(l)

Now run pyjsbuild hello.py to generate a plain Javascript
application: pyjs creates an ./output folder containing all files
you need to move to your webspace later. Of course you can test locally,
too.

Add 3 additional lines in total and your application can run with both
Pyjs (i.e. plain Javascript) and Pyjs Desktop:

import pyjd # this is dummy in pyjs
from pyjamas.ui.RootPanel import RootPanel
from pyjamas.ui.Label import Label
pyjd.setup('public/hello.html')
l = Label('Hello Pyjs')
RootPanel().add(l)
pyjd.run()

Execute pyjd hello.py, or python hello.py, to run
the very same application native on Python, giving you a Python stack trace on
errors. Pyjs Desktop gives you much more control making testing and debugging
a piece of a cake. No more web development pain – hooray!
Note the hello.html file referenced above: this is a container
for your application generated by Pyjs that you can adjust to your needs.