pymonkey — Access SpiderMonkey from Python

This module offers a low-level interface to the Mozilla SpiderMonkey JavaScript engine.

exception pymonkey.error

This is the type of any SpiderMonkey-related errors thrown by this module.

pymonkey.undefined

This is the singleton that represents the JavaScript value undefined, as Python has no equivalent representation (JavaScript’s null is mapped to Python’s None object). For instance:

>>> cx = pymonkey.Runtime().new_context()
>>> cx.evaluate_script(cx.new_object(), '', '<string>', 1)
<type 'pymonkey.undefined'>

Unfortunately, this object currently does not have a “falsy” value, e.g.:

>>> if pymonkey.undefined:
...   print 'Huh, this is kind of unintuitive.'
Huh, this is kind of unintuitive.

The reason for this is simply that we don’t currently know how to make this object have a falsy value, if it’s even possible.

class pymonkey.Object

This is the type of JavaScript objects. Such objects can only be created via Pymonkey calls like Context.new_object() or through the execution of JS code, but this type object can be used with Python’s built-in isinstance() to verify that an object is a JS object, like so:

>>> obj = pymonkey.Runtime().new_context().new_object()
>>> isinstance(obj, pymonkey.Object)
True

class pymonkey.Context

This is the type of JavaScript context objects. Contexts can only be created via a call to Runtime.new_context(), but this type object can be used with Python’s built-in isinstance() to verify that an object is a context, like so:

>>> cx = pymonkey.Runtime().new_context()
>>> isinstance(cx, pymonkey.Context)
True

class pymonkey.Runtime

Creates a new JavaScript runtime. JS objects created by the runtime may only interact with other JS objects of the same runtime.

new_context()

Creates a new Context object and returns it. Contexts are best conceptualized as threads of execution in a JS runtme; each one has a program counter, a current exception state, and so forth. JS objects may be freely accessed and changed by contexts that are associated with the same JS runtime as the objects.