
MacPython OSA Modules
*********************

This chapter describes the current implementation of the Open
Scripting Architecture (OSA, also commonly referred to as AppleScript)
for Python, allowing you to control scriptable applications from your
Python program, and with a fairly pythonic interface. Development on
this set of modules has stopped, and a replacement is expected for
Python 2.5.

For a description of the various components of AppleScript and OSA,
and to get an understanding of the architecture and terminology, you
should read Apple's documentation. The "Applescript Language Guide"
explains the conceptual model and the terminology, and documents the
standard suite. The "Open Scripting Architecture" document explains
how to use OSA from an application programmers point of view. In the
Apple Help Viewer these books are located in the Developer
Documentation, Core Technologies section.

As an example of scripting an application, the following piece of
AppleScript will get the name of the frontmost **Finder** window and
print it:

   tell application "Finder"
       get name of window 1
   end tell

In Python, the following code fragment will do the same:

   import Finder

   f = Finder.Finder()
   print f.get(f.window(1).name)

As distributed the Python library includes packages that implement the
standard suites, plus packages that interface to a small number of
common applications.

To send AppleEvents to an application you must first create the Python
package interfacing to the terminology of the application (what
**Script Editor** calls the "Dictionary"). This can be done from
within the **PythonIDE** or by running the ``gensuitemodule.py``
module as a standalone program from the command line.

The generated output is a package with a number of modules, one for
every suite used in the program plus an ``__init__`` module to glue it
all together. The Python inheritance graph follows the AppleScript
inheritance graph, so if a program's dictionary specifies that it
includes support for the Standard Suite, but extends one or two verbs
with extra arguments then the output suite will contain a module
``Standard_Suite`` that imports and re-exports everything from
``StdSuites.Standard_Suite`` but overrides the methods that have extra
functionality. The output of ``gensuitemodule`` is pretty readable,
and contains the documentation that was in the original AppleScript
dictionary in Python docstrings, so reading it is a good source of
documentation.

The output package implements a main class with the same name as the
package which contains all the AppleScript verbs as methods, with the
direct object as the first argument and all optional parameters as
keyword arguments. AppleScript classes are also implemented as Python
classes, as are comparisons and all the other thingies.

The main Python class implementing the verbs also allows access to the
properties and elements declared in the AppleScript class
"application". In the current release that is as far as the object
orientation goes, so in the example above we need to use
``f.get(f.window(1).name)`` instead of the more Pythonic
``f.window(1).name.get()``.

If an AppleScript identifier is not a Python identifier the name is
mangled according to a small number of rules:

* spaces are replaced with underscores

* other non-alphanumeric characters are replaced with ``_xx_`` where
  ``xx`` is the hexadecimal character value

* any Python reserved word gets an underscore appended

Python also has support for creating scriptable applications in
Python, but The following modules are relevant to MacPython
AppleScript support:

* ``gensuitemodule`` --- Generate OSA stub packages
* ``aetools`` --- OSA client support
* ``aepack`` --- Conversion between Python variables and AppleEvent
  data containers
* ``aetypes`` --- AppleEvent objects
* ``MiniAEFrame`` --- Open Scripting Architecture server support
  * AEServer Objects
In addition, support modules have been pre-generated for ``Finder``,
``Terminal``, ``Explorer``, ``Netscape``, ``CodeWarrior``,
``SystemEvents`` and ``StdSuites``.
