8.1 Extending PyS60

The general rules and guidelines for writing Python extensions apply in the S60 Python environment as well.

The steps for the implementation of an extension modules include:

Preparation of the data structures that make the C/C++ coded extensions visible to the Python interpreter and make it possible to perform calls from Python to C/C++ code
Conversions between C/C++ representations of the Python objects and object types used in the extension code
Maintenance of the reference counts of the C/C++ representations of the Python objects
Passing of exceptions between C/C++ code and Python
Management of interpreter's thread state and the interpreter lock

In addition to the concerns common for all Python C extensions, the following principles should be considered when implementing new Python interfaces in the S60 environment:

Maximize the usage of Python's built-in types at the interfaces.
Related to the above: design interfaces in such a way that information can be passed between them with minimal conversions.
Convert Symbian operating system exceptions or errors to Python exceptions.
Unicode strings are used at the interfaces to represent text that gets shown on the GUI. They can be passed to and from Symbian operating system without conversions.
While performing potentially long-lasting or blocking calls from an extension implementation to services outside the interpreter, the interpreter lock must be released and then re-acquired after the call.
Rather than always implementing a thin wrapper on top of a Symbian OS facility, consider the actual task for which the script writer needs the particular interface. For example, if the task involves interaction with the users using the GUI, the script writer's interest may well be limited to performing the interaction or information exchange in a way that is compatible with the UI style rather than having full control of the low-level details of the GUI implementation.
The C/C++ implementation of a Python interface should be optimized for performance and covering access to the necessary features of the underlying Platform. Where necessary, the Python programming interface can be further refined by wrapper modules written in Python.

The pyd name should be of the format 'kf_<module-name>.pyd'. Note that this change is required only for the pyd name and module name is not required to have this prefix.

The module initialization function must be exported at ordinal 1. The module identification is based on the filename only. As a special feature of PyS60, an optional module finalizer function may be exported at ordinal 2.

The extension modules added by the developer should be placed in the module repo folder of the PyS60 Application Packager so that the compiled PYD's can be picked up while packaging. For information on this topic refer 8.1.3, Distributing Extension Modules.

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