Rapid GUI Programming with Python and Qt

1. Rapid GUI Programmingwith Python and Qt Classes and Modules By Raed S. Rasheed

2. Classes and Modules Python fully supports procedural and object-oriented programming The syntax for creating a class is simple: class className(base_classes): suite

3. Creating Instances • Python has the __new__() special method which is called to construct an object, • the __init__() special method which is called to initialize a newly constructed object. • When an object is about to be garbage-collected its __del__() special method is called, with self as its only argument. We will create one that stores a string (the name of a kind of chair) and a number (how many legs the chair has): class Chair(object): """This class represents chairs.""" def __init__(self, name, legs=4): self.name = name self.legs = legs

4. Creating Instances To create an instance of a class, we use the following syntax: instance = className(arguments) for example: chair1 = Chair("Barcelona") chair2 = Chair("Bar Stool", 1) Since the attributes are public, they can be read or assigned to using the dot (.) operator; for example: print chair2.name will print “Bar Stool”, and chair1.legs = 2 will change chair1’s legs attribute’s value from 4 to 2.

5. Methods and Special Methods class Rectangle(object): def __init__(self, width, height): self.width = width self.height = height defgetWidth(self): return self.width defsetWidth(self, width): self.width = width defgetHeight(self): return self.height defsetHeight(self, height): self.height = height def area(self): return self.getWidth() * self.getHeight()

6. Methods and Special Methods rect= Rectangle(50, 10) print rect.area() # Prints "500" rect.setWidth(20)

7. Methods and Special Methods property() function class Rectangle(object): def __init__(self, width, height): self.width = width self.height = height def _area(self): return self.width * self.height area = property(fget=_area)

8. Methods and Special Methods rect= Rectangle(5, 4) print rect.width, rect.height, rect.area # Prints (5, 4, 20) rect.width = 6

9. Methods and Special Methods def_width(self): return self.__width def _setWidth(self, width): # Perform some computation self.__width = width width = property(fget=_width, fset=_setWidth)

10. Methods and Special Methods class Rectangle(object): def__init__(self, width, height): self.__width = width self.__height = height def_area(self): return self.__width * self.__height area = property(fget=_area) def_height(self): return self.__height def_setHeight(self, height): self.__height = height height = property(fget=_height, fset=_setHeight) 

11. Methods and Special Methods def _width(self):        return self.__width def _setWidth(self, width):        self.__width = width    width = property(fget=_width, fset=_setWidth) def __cmp__(self, other): return cmp(self.area, other.area) def __nonzero__(self): return self.__width or self.__height def __repr__(self): return "Rectangle(%d, %d)" % (self.__width, self.__height)

12. Methods and Special Methods print ("Starting..\n") rect1 = Rectangle(4,5) print ("Area is [",rect1.area,"]") print ("Set width to [ 7 ] and height to [ 2 ]") rect1.width = 7 rect1.height = 2 print ("Now area is [",rect1.area,"]") print ("\nFinishing..")

13. Methods and Special Methods Output:- Starting.. Area is [ 20 ] Set width to [ 7 ] and height to [ 2 ] Now area is [ 14 ] Finishing..

14. Methods and Special Methods Method Syntax Description __init__(self, args) x = X() Initializes a newly created instance __call__(self, args) x() Makes instances callable, that is,turns them into functors. The args are optional. __cmp__(self, other) x == y x < y # etc Returns -1 if self < other, 0 if they are equal, and 1 otherwise. If __cmp__() is implemented, it will be used for any comparison operators that are not explicitly implemented. __eq__(self, other) x == y Returns True if x is equal to y __ne__(self, other) x != y Returns True if x is not equal to y __le__(self, other) x <= y Returns True if x is less than or equal to y

15. Methods and Special Methods Method Syntax Description __lt__(self, other) x < y Returns True if x is less than y __ge__(self, other) x >= y Returns True if x is greater than or equal to y __gt__(self, other) x > y Returns True if x is greater than y __nonzero__(self) if x: pass Returns True if x is nonzero __repr__(self) y = eval(`x`) Returns an eval()-able representation of x. Using backticks is the same as calling repr(). __str__(self) print x Returns a human-readable representation of x __unicode__(self) print x Returns a human-readable Unicode representation of x

16. Methods and Special Methods def __cmp__(self, other): return cmp(self.area(), other.area()) rectA = Rectangle(4, 4) rectB = Rectangle(8, 2) rectA == rectB # True because both have the same area rectA < rectB # False def __cmp__(self, other): if (self.width != other.width): return cmp(self.width, other.width) return cmp(self.height, other.height)

17. Methods and Special Methods def__nonzero__(self): return self.width or self.height) def __repr__(self): return "Rectangle(%d, %d)" % (self.width, self.height)

18. Methods and Special Methods Method Syntax Method Syntax __float__(self) float(x) __int__(self) int(x) __abs__(self) abs(x) __neg__(self) -x __add__(self, other) x + y __sub__(self, other) x - y __iadd__(self, other) x +=y __isub__(self, other) x -= y __radd__(self, other) y + x __rsub__(self, other) y - x __mul__(self, other) x * y __mod__(self, other) x % y __imul__(self, other) x *= y __imod__(self, other) x %= y __rmul__(self, other) y * x __rmod__(self, other) y % x __floordiv__(self, other) x // y __truediv__(self, other) x / y __ifloordiv__(self, other) x //= y __itruediv__(self, other) x /= y __rfloordiv__(self, other) y // x __rtruediv__(self, other) y / x

19. Static Data, and Static Methods and Decorators class Balloon(object): unique_colors = set() def __init__(self, color): self.color = color Balloon.unique_colors.add(color) @staticmethod defuniqueColorCount(): return len(Balloon.unique_colors) @staticmethod defuniqueColors(): return Balloon.unique_colors.copy()

20. Static Data, and Static Methods and Decorators class Example: staticVariable = 5 print("starting\n") # Access through class print (Example.staticVariable) # prints 5 # Access through instance instance = Example() print (instance.staticVariable) # still 5

21. Static Data, and Static Methods and Decorators # Change within instance instance.staticVariable = 6 print (instance.staticVariable) # 6 print (Example.staticVariable) # 5 # Change through class Example.staticVariable = 7 print (instance.staticVariable) # still 6 print (Example.staticVariable) # now 7 print("\nfinishing")

22. Static Data, and Static Methods and Decorators class Example(object): name = "Example" @staticmethod def static(): print ("%s static() called" % Example.name) class Offspring1(Example): name = "Offspring1"

23. Static Data, and Static Methods and Decorators class Offspring2(Example): name = "Offspring2" @staticmethod def static(): print ("%s static() called" % Example.name) print("starting\n") Example.static() # prints Example Offspring1.static() # prints Example Offspring2.static() # prints Offspring2 print("\nfinishing“)

24. Static Data, and Static Methods and Decorators class Example: name = "Example" @classmethod def static(cls): print ("%s static() called" % cls.name) class Offspring1(Example): name = "Offspring1" pass

25. Static Data, and Static Methods and Decorators class Offspring2(Example): name = "Offspring2" @classmethod def static(cls): print ("%s static() called" % cls.name) print("starting\n") Example.static() # prints Example Offspring1.static() # prints Offspring1 Offspring2.static() # prints Offspring2 print("\nfinishing")

26. Inheritance and Polymorphism class Item(object): def __init__(self, artist, title, year=None): self.__artist = artist self.__title = title self.__year = year def artist(self): return self.__artist defsetArtist(self, artist): self.__artist = artist def title(self): return self.__title

27. Inheritance and Polymorphism deftitle(self): return self.__title defsetTitle(self, title): self.__title = title def year(self): return self.__year defsetYear(self, year): self.__year = year def __str__(self): year = "" if self.__year is not None: year = " in %d" % self.__year return "%s by %s%s" % (self.__title, self.__artist, year)

28. Inheritance and Polymorphism class Painting(Item): def __init__(self, artist, title, year=None): super(Painting, self).__init__(artist, title, year) # item.__init__(self, artist, title, year) class Sculpture(Item): def __init__(self, artist, title, year=None, material=None): super(Sculpture, self).__init__(artist, title, year) self.__material = material

29. Inheritance and Polymorphism defmaterial(self): return self.__material defsetMaterial(self, material): self.__material = material def __str__(self): materialString = "" if self.__material is not None: materialString = " (%s)" % self.__material return "%s%s" % (super(Sculpture, self).__str__(), materialString)

30. Inheritance and Polymorphism class Title(object): def __init__(self, title) self.__title = title def title(self): return self.__title return "%s%s" % (super(Sculpture, self).__str__(), materialString)

31. Inheritance and Polymorphism items = [] items.append(Painting("Cecil Collins", "The Poet", 1941)) items.append(Sculpture("Auguste Rodin", "Naked Balzac", 1917, "plaster")) items.append(Title("Eternal Springtime")) for item in items: print item.title()