Ubuntu – How to write Appindicators in python

Good question.

First of all, the appindicators are not Unity specific in any way. Actually, they run just as well on Xfce or KDE. It's very, very, simple to use. You'll create an indicator object, set the name of icons to use when it needs attention, etc, and simply attach menus to it. The indicators are then sent over dbus and properly displayed in a manner suitable for the current desktop environment. In Unity, Gnome Shell, Xfce and LXDE, it'll be displayed as GTK menus, and in KDE it'll be displayed as Qt menus, etc. Very neat. You can find more information about it here: http://unity.ubuntu.com/projects/appindicators/

In the right pane of Glade, you have a Signals page under Properties. Here you can simply type the name of the method to use as handler for that signal. In your code, you'll just create a gtk.Builder object, load the XML that Glade produces and use the gtk.Builder.connect_signals method to connect all your signals to their methods. This means you can use Glade interfaces in almost any programming language. Since that is so easy, and since languages are different by nature, it makes little sense to add coding to Glade itself. For coding Python (and other languages), I will recommend having a look at Geany ( http://apt.ubuntu.com/p/geany). It is a very good editor/IDE.

Other things in Unity are so new, there is little documentation, except as code examples. Some of the APIs are just now becoming stable, such as for Scopes and Lenses, which weren't even called that a little while ago. As a beginner, I'd wait a little bit before looking into those things.

The entries on the launcher, are actually just referred to as LauncherEntry in code, and it can use a progress bar, a counter and QuickLists. I haven't actually coded that myself, but this page has an example and it seems very easy, like the rest of the Unity APIs: http://bazaar.launchpad.net/~unity-team/libunity/trunk/view/head:/examples/launcher.py

Both PyQt4 and PySide have very similar mappings to the Qt API. There are, however, some differences, my opinions on which are described below:

Maintenance

They are both well maintained. The PySide produces a lot more regular releases at the moment: I think it's more closely linked to Qt than PyQt4 and as a newer project has a more active community at the moment. However, that is just my impression and it may be wrong.

PyQt4 has the option of commercial support available (I don't know whether this is true for PySide or not).

Licence

PyQt4 is released under either a commercial licence or the GPL; PySide is released under the LGPL. For commercial applications, this is a significant difference.

APIs and Python versions

PyQt4 supports two different APIs. API version 1 is the default for python 2.x applications and API version 2 is the default for python 3.x applications.

PySide only supports one API, which is roughly equivalent to PyQt4's API version 2. API version 2 (or the PySide API) is much nicer to work with than PyQt4's API version 1. In API version 1 you have a lot of code that casts python strings to QtCore.QStrings and back again. In API version 2 (and PySide) you just use python strings throughout. See below for a simple way of switching between PyQt4 and PySide if you want to play with both.

Most code I write seems to work equally well in PyQt4 and PySide. Historically, I had always used PyQt4 for python GUIs but most new stuff I write now uses PySide (mainly due to the more flexible licensing). I'd certainly recommend you try both and see how you find them. If you use QtVariant.py (below), switching between them is trivial and when you make a decision there will only be one file that needs updating.

Documentation

The documentation for both PyQt4 and PySide are auto-generated from the main Qt documentation. In my opinion, the PySide documentation is a better representation of what you actually use, but in practice I tend to just use the Qt documentation anyway (it's quite easy to mentally translate the C++ documentation to python).

External Libraries

If you're using external libraries, some do not work with PySide yet. There aren't many that you need to work with PySide to be honest, but a couple of years ago I wrote some code that used twisted (with the Qt reactor) and matplotlib and that forced me down the line of using PyQt4 rather than PySide. I think it's quite likely that these libraries will have been updated to support both by now, but I haven't checked.

Making Code work with either PyQt4 or PySide

Assuming you're using python 2.x, you can fairly easily make your code compatible with both PySide and PyQt4 by making a QtVariant.py and using:

from QtVariant import QtGui, QtCore

or whatever. The QtVariant.py that I use looks like this:

import sys
import os

default_variant = 'PySide'

env_api = os.environ.get('QT_API', 'pyqt')
if '--pyside' in sys.argv:
    variant = 'PySide'
elif '--pyqt4' in sys.argv:
    variant = 'PyQt4'
elif env_api == 'pyside':
    variant = 'PySide'
elif env_api == 'pyqt':
    variant = 'PyQt4'
else:
    variant = default_variant

if variant == 'PySide':
    from PySide import QtGui, QtCore
    # This will be passed on to new versions of matplotlib
    os.environ['QT_API'] = 'pyside'
    def QtLoadUI(uifile):
        from PySide import QtUiTools
        loader = QtUiTools.QUiLoader()
        uif = QtCore.QFile(uifile)
        uif.open(QtCore.QFile.ReadOnly)
        result = loader.load(uif)
        uif.close()
        return result
elif variant == 'PyQt4':
    import sip
    api2_classes = [
            'QData', 'QDateTime', 'QString', 'QTextStream',
            'QTime', 'QUrl', 'QVariant',
            ]
    for cl in api2_classes:
        sip.setapi(cl, 2)
    from PyQt4 import QtGui, QtCore
    QtCore.Signal = QtCore.pyqtSignal
    QtCore.QString = str
    os.environ['QT_API'] = 'pyqt'
    def QtLoadUI(uifile):
        from PyQt4 import uic
        return uic.loadUi(uifile)
else:
    raise ImportError("Python Variant not specified")

__all__ = [QtGui, QtCore, QtLoadUI, variant]