ZetCode PyQt4 tutorial Drag and Drop

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial

This is a simple drag and
drop example. 

author: Jan Bodnar
website: zetcode.com
last edited: January 2015
"""

import sys
from PyQt4 import QtGui

# In order to drop text on the QtGui.QPushButton widget, we must reimplement some methods. Therefore, we create our own Button class which inherits from the QtGui.QPushButton class.
class Button(QtGui.QPushButton):

    def __init__(self, title, parent):
        super(Button, self).__init__(title, parent)

        # We enable drop events for the widget.
        self.setAcceptDrops(True)

    # First, we reimplement the dragEnterEvent() method. We inform about the data type that we accept. In our case it is plain text.
    def dragEnterEvent(self, e):

        if e.mimeData().hasFormat('text/plain'):
            e.accept()
        else:
            e.ignore() 

    # By reimplementing the dropEvent() method we define what we will do upon the drop event. Here we change the text of the button widget.
    def dropEvent(self, e):
        self.setText(e.mimeData().text()) 

class Example(QtGui.QWidget):

    def __init__(self):
        super(Example, self).__init__()

        self.initUI()

    def initUI(self):

        edit = QtGui.QLineEdit('', self)
        # The QtGui.QLineEdit widget has a built-in support for drag operations. All we need to do is to call setDragEnabled() method to activate it.
        edit.setDragEnabled(True)
        edit.move(30, 65)

        button = Button("Button", self)
        button.move(190, 65)

        self.setWindowTitle('Simple drag & drop')
        self.setGeometry(300, 300, 300, 150)

def main():

    app = QtGui.QApplication(sys.argv)
    ex = Example()
    ex.show()
    app.exec_()  

if __name__ == '__main__':
    main()   

--------------------------------------------------------------------------------

#!/usr/bin/python
# -*- coding: utf-8 -*-

"""
ZetCode PyQt4 tutorial

In this program, we can press on a button
with a left mouse click or drag and drop the
button with  the right mouse click. 

author: Jan Bodnar
website: zetcode.com
last edited: October 2013
"""

import sys
from PyQt4 import QtCore, QtGui

# We create a Button class which will derive from the QtGui.QPushButton. We also reimplement two methods of the QtGui.QPushButton: the mouseMoveEvent() and the mousePressEvent(). The mouseMoveEvent() method is the place where the drag & drop operation begins.
class Button(QtGui.QPushButton):

    def __init__(self, title, parent):
        super(Button, self).__init__(title, parent)

    def mouseMoveEvent(self, e):

        # Here we decide that we can perform drag & drop only with a right mouse button. The left mouse button is reserved for clicking on the button.
        if e.buttons() != QtCore.Qt.RightButton:
            return

        # The QDrag object is created. The class provides support for MIME-based drag and drop data transfer.
        mimeData = QtCore.QMimeData()

        drag = QtGui.QDrag(self)
        drag.setMimeData(mimeData)
        drag.setHotSpot(e.pos() - self.rect().topLeft())

        # The start() method of the drag object starts the drag & drop operation.
        dropAction = drag.start(QtCore.Qt.MoveAction)

    # We print 'press' to the console if we left click on the button with the mouse. Notice that we call mousePressEvent() method on the parent as well. Otherwise, we would not see the button being pushed.
    def mousePressEvent(self, e):

        super(Button, self).mousePressEvent(e)

        if e.button() == QtCore.Qt.LeftButton:
            print 'press'

class Example(QtGui.QWidget):

    def __init__(self):
        super(Example, self).__init__()

        self.initUI()

    def initUI(self):

        self.setAcceptDrops(True)

        self.button = Button('Button', self)
        self.button.move(100, 65)

        self.setWindowTitle('Click or Move')
        self.setGeometry(300, 300, 280, 150)
        self.show()

    def dragEnterEvent(self, e):

        e.accept()

    def dropEvent(self, e):

        # In the dropEvent() method we code what happens after we release the mouse button and finish the drop operation. We find out the current mouse pointer position and move the button accordingly.
        position = e.pos()
        self.button.move(position)

        # We specify the type of the drop action. In our case it is a move action.
        e.setDropAction(QtCore.Qt.MoveAction)
        e.accept()

def main():

    app = QtGui.QApplication([])
    ex = Example()
    sys.exit(app.exec_())

if __name__ == '__main__':
    main()