PyQt: rapid application development

1. PyQt Rapid Application Development
Lorenzo Mancini (lmancini@develer.com)

2. Qt and C++
 Qt is a wonderful piece of software
 Application multi-platform portability layer
 Lots of modules and features
 But... it exposes a C++ API

3. What's wrong with C++?
 Compile/run workflow
 Manual memory management
 (Few) testing facilities
 Wrong frame of mind
 Steep learning curve

4. Learning C++ in 21 days

5. 2 words about Python
 Object-oriented language
 Automatic memory management
 Language uses strong/dynamic typing
 Objects have types, references don't
 Code is compiled on-the-fly
 No compile/run workflow
 Easy to pick up

6. Learning Python in 21 14 days

7. What is PyQt
 A binding that maps every Qt class to a
Python class
 It's not Qt rewritten in Python
 → Easy to keep in sync with Qt
 Developed by Riverbank Software (UK
based)
 Qt's feature set + Python development
speed = profit!

8. First PyQt program
from PyQt4.Qt import *
app = QApplication([])
l = QLabel(“Hello world!”)
l.show()
app.exec_()

9. Signal/slot
 Any Python callable can be a slot!
from PyQt4.Qt import *
app = QApplication([])
pb = QPushButton("Click me!")
pb.show()
def cb():
pb.setText("CLICKED!")
QObject.connect(pb, SIGNAL("clicked(bool)"), cb)
app.exec_()

10. A simple text editor
Live demo

11. Reality check
 CAD/CAM for fashion design
 Uses PyQt from day 1
 200000 LOC codebase (including tests)
 In production since 2008, actively mantained
 Medical appliance control panel
 Full rewrite of a 1 man-year C++ application
become unmaintenable
 Development completed in 3 man months
 ...many others

12. PyQt licensing
 Qt: GPL / LGPL / commercial
 PyQt: GPL (no LGPL!)
 → PyQt GPL:
 ok for internal tools
 ok for open-source software
 Otherwise: PyQt commercial license

13. Urban myths
 “Python is too slow to develop real
applications!”
 FALSE: In a typical PyQt application, the bulk of
the running code is “inside” Qt, hence running
at C++ speed.
 “I must distribute the Python interpreter
along with my program source!”
 FALSE: you can package your application
(PyInstaller), then bundle into a nice graphical
installer (InnoSetup)

14. THANKS !
Develer S.r.l.
Via Mugellese 1/A
50013 Campi Bisenzio
Firenze - Italy
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