Python Bindings for KDE (PyKDE-3.3.16.0)
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General Limitations

Python Strings, Qt Strings and Unicode

Unicode support was added to Qt in v2.0 and to Python in v1.6. In Qt, Unicode -support is implemented using the TQString class. It is -important to understand that TQStrings, Python string objects -and Python Unicode objects are all different but conversions between them are -automatic in many cases and easy to achieve manually when needed.

Whenever PyKDE expects a TQString as a function argument, a -Python string object or a Python Unicode object can be provided instead, and -PyKDE will do the necessary conversion automatically.

You may also manually convert Python string and Unicode objects to -TQStrings by using the TQString constructor -as demonstrated in the following code fragment.

qs1 = TQString('Converted Python string object')
-qs2 = TQString(u'Converted Python Unicode object')

In order to convert a TQString to a Python string object use -the Python str() function. Applying -str() to a null TQString and an empty -TQString both result in an empty Python string object.

In order to convert a TQString to a Python Unicode object use -the Python unicode() function. Applying -unicode() to a null TQString and an empty -TQString both result in an empty Python Unicode object.

Access to Protected Member Functions

When an instance of a C++ class is not created from Python it is not possible -to access the protected member functions, or emit the signals, of that -instance. Attempts to do so will raise a Python exception. Also, any Python -methods corresponding to the instance's virtual member functions will never be -called.

Garbage Collection

C++ does not garbage collect unreferenced class instances, whereas Python does. -In the following C++ fragment both colours exist even though the first can no -longer be referenced from within the program:

c = TQColor();
-c = TQColor();

In the corresponding Python fragment, the first colour is destroyed when -the second is assigned to c:

c = TQColor()
-c = TQColor()

In Python, each colour must be assigned to different names. Typically this -is done within class definitions, so the code fragment would be something like:

self.c1 = TQColor()
-self.c2 = TQColor()

Sometimes a Qt class instance will maintain a pointer to another instance and -will eventually call the destructor of that second instance. The most common -example is that a TQObject (and any of its sub-classes) keeps -pointers to its children and will automatically call their destructors. In -these cases, the corresponding Python object will also keep a reference to the -corresponding child objects.

So, in the following Python fragment, the first TQLabel is -not destroyed when the second is assigned to l because the -parent TQWidget still has a reference to it.

p = TQWidget()
-l = TQLabel('First label',p)
-l = TQLabel('Second label',p)

C++ Variables

Access to C++ variables is supported. They are accessed as Python instance -variables. For example:

tab = TQTab()
-tab.label = "First Tab"
-tab.r = TQRect(10,10,75,30)

Global variables and static class variables are effectively read-only. They -can be assigned to, but the underlying C++ variable will not be changed. This -may change in the future.

Access to protected C++ class variables is not supported. This may change in -the future.

Multiple Inheritance

It is not possible to define a new Python class that sub-classes from more than -one Qt class.

tr() methods

-In a normal Qt installation, every descendant of TQObject inherits two methods -(tr (const char *) and tr (const char *, const char *) from TQObject explicitly -and also overloads these methods via the moc mechanism (by defining Q_OBJECT -in the class declaration). KDE however is compiled with -DQT_NO_TRANSLATION, -which prevents moc from creating the overloading tr() methods, and also produces -side-effects with a normal Qt installation which was compiled without the --DQT_NO_TRANSLATION switch. -

-PyKDE handles this situation by NOT providing tr() methods (either the inherited -methods from TQObject or the moc generated methods) for any KDE based QObject -descendant. The tr() methods are static, so TQObject::tr () methods are available -via PyQt, as are tr() methods for any PyQt TQObject descendant. PyKDE's handling -of these methods has no effect on PyQt. -

Instead of the tr() methods, KDE uses corresponding i18n() methods for translating. -These methods are available in the kdecore module of PyKDE. For compatibility with -KDE, you should use the i18n methods. -

Socket classes

-Most of their functionality already exists in the Python socket class or in the -KSocket class (kdecore module). These classes may be implemented at a future date -(they require support for C socket structures and careful handling to avoid buffer -overflow problems/exploits) -

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