Overview.rest

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:

[[assets/images/overview.png]]

[[/assets/images/overview.png]]

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. Note the hello.html file referenced above: this is a container for your application generated by Pyjs that you can adjust to your needs.

Ready for more? [[Let's get started|GettingHelp]]!