PyExecJS (EOL)

EOL

Run JavaScript code from Python.

PyExecJS is a porting of ExecJS from Ruby. PyExecJS automatically picks the best runtime available to evaluate your JavaScript program.

A short example:

import execjs
execjs.eval("'red yellow blue'.split(' ')")
>>> ['red', 'yellow', 'blue']
ctx = execjs.compile("""
     function add(x, y) {
         return x + y;
     }
 """)
 ctx.call("add", 1, 2)
 >>> 3

Supported runtimes

First-class support (runtime class is provided and tested)

• PyV8 - A python wrapper for Google V8 engine,
• Node.js
• PhantomJS
• Nashorn - Included with Oracle Java 8

Second-class support (runtime class is privided but not tested)

• Apple JavaScriptCore - Included with Mac OS X
• Microsoft Windows Script Host (JScript)
• SlimerJS
• Mozilla SpiderMonkey

Installation

$ pip install PyExecJS

Details

If EXECJS_RUNTIME environment variable is specified, PyExecJS pick the JavaScript runtime as a default:

>>> execjs.get().name # this value is depends on your environment.
>>> os.environ["EXECJS_RUNTIME"] = "Node"
>>> execjs.get().name
'Node.js (V8)'

You can choose JavaScript runtime by execjs.get():

>>> default = execjs.get() # the automatically picked runtime
>>> default.eval("1 + 2")
3
>>> import execjs.runtime_names
>>> jscript = execjs.get(execjs.runtime_names.JScript)
>>> jscript.eval("1 + 2")
3
>>> import execjs.runtime_names
>>> node = execjs.get(execjs.runtime_names.Node)
>>> node.eval("1 + 2")
3

The pros of PyExecJS is that you do not need take care of JavaScript environment. Especially, it works in Windows environment without installing extra libraries.

One of cons of PyExecJS is performance. PyExecJS communicate JavaScript runtime by text and it is slow. The other cons is that it does not fully support runtime specific features.

PyV8 might be better choice for some use case.

Changelog

1.0.0

• First release.