Updated: March 31, 2006 for release 0.8.2
Resource files are an old idea, but they are not widely used in the Python community. My own experience with resources is based largely on how Mac applications used the resource fork. PythonCard separates the window, component layout, menu descriptions, and strings from the source code by putting them in a separate .rsrc.py file. This allows the layout to be modified independently of the source code and logic of the application. It also simplifies supporting multiple layouts for different OS platforms or doing international versions of an application. Finally, it means that a non-programmer can handle the layout since they do not need to write any Python code.
The resource file typically shares the same base name as the main application, so the minimal sample has two files:
The resource file has a .py extension because the resource file is actually a valid Python dictionary and so it is easy to edit and validate the resource file using a Python-aware editor. The files are plain text. They are not in XML format since a separate program would be necessary to validate the XML and I feel that XML is less human-readable than the equivelant nested dictionary/list done using Python syntax.
For the most part, it is no longer necessary to edit resource files in a text editor, instead you can use the resourceEditor sample to change the layout and menus for a PythonCard application.
Note that once the resource file attributes are frozen we will likely switch to XML for the resource format to improve interop with other layout tools. [Since we're approaching a 1.0 release of PythonCard, I think this is unlikely, but I'll leave this comment in for the time being. - Kevin Altis]
Binary data necessary for an application such as images and sound files are stored separately. Images necessary for the application components are referenced via 'image' or 'file' attributes in the resource file.
It is possible to have a fairly short edit/run cycle by keeping the layout of your app open in the resourceEditor (layout editor) and the source code open in the codeEditor or your favorite editor/IDE and then launching the app using the Run command under the File menu or from the command-line or a directory browser (Explorer) as you make changes. If you have an error in your source that prevents the app from running, you can use the "Run with interpreter" command and the interpreter will be left open showing you where the error occurred in your source.
The organization of the resource file is defined by the spec classes in component.py, spec.py, widget.py, and each component module. When a resource is read in (see resource.py) it is validated against the specs, default arguments are initialized and any undefined component types in the resource will cause a runtime error. The resource dictionary is converted to an object that supports dot notation automatically and most places in the framework where a resource argument is used, it is valid to pass in a dictionary instead.
The noresource sample shows an example of a PythonCard application that does not have a resource file. The noresource sample also shows an example of dynamic component creation when the application starts up.
| General Concepts and Limitations | Components | Dialogs | Events and Handlers | Menus | Resource Files | Runtime Tools
$Revision: 1.5 $ : $Author: alextweedly $ : Last updated $Date: 2006/04/06 11:00:26 $