initial

Author: fpierfed

00-start.py

@@ -0,0 +1,39 @@
+from math import pi
+
+
+class Point:
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+    def move_by(self, dx, dy):
+        self.x += dx
+        self.y += dy
+
+    def __str__(self):
+        return f'A Point at {self.x}, {self.y}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.x}, {self.y})'
+
+
+class Circle:
+    def __init__(self, center, radius):
+        self.center = center
+        self.radius = radius
+
+    @property
+    def area(self):
+        return pi * self.radius ** 2
+
+    def __str__(self):
+        return f'A Circle at {self.center.x}, {self.center.y} and ' + \
+               f'radius {self.radius}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.center!r}, {self.radius!r})'
+
+
+# What about this?
+# p = Point('1', '2')
+# p.move_by('10, '20')

01-properties.py

@@ -0,0 +1,74 @@
+from math import pi
+
+
+class Point:
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+    @property
+    def x(self):
+        return self._x
+
+    @x.setter
+    def x(self, value):
+        assert isinstance(value, int), 'Booooo! Expecting an int'
+        self._x = value
+
+    @property
+    def y(self):
+        return self._y
+
+    @y.setter
+    def y(self, value):
+        assert isinstance(value, int), 'Booooo! Expecting an int'
+        self._y = value
+
+    def move_by(self, dx, dy):
+        self.x += dx
+        self.y += dy
+
+    def __str__(self):
+        return f'A Point at {self.x}, {self.y}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.x}, {self.y})'
+
+
+class Circle:
+    def __init__(self, center, radius):
+        self.center = center
+        self.radius = radius
+
+    @property
+    def center(self):
+        return self._center
+
+    @center.setter
+    def center(self, value):
+        assert isinstance(value, Point), 'Booooo! Expecting a Point'
+        self._center = value
+
+    @property
+    def radius(self):
+        return self._radius
+
+    @radius.setter
+    def radius(self, value):
+        assert isinstance(value, int), 'Booooo! Expecting an int'
+        self._radius = value
+
+    @property
+    def area(self):
+        return pi * self.radius ** 2
+
+    def __str__(self):
+        return f'A Circle at {self.center.x}, {self.center.y} and ' + \
+               f'radius {self.radius}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.center!r}, {self.radius!r})'
+
+
+# Lots of code!
+# Tedious to modify

02-property_macro.py

@@ -0,0 +1,59 @@
+from math import pi
+
+
+def check_type(name, required_type):
+    variable_name = f'_{name}'
+
+    @property
+    def variable(self):
+        return getattr(self, variable_name)
+
+    @variable.setter
+    def variable(self, value):
+        assert isinstance(value, required_type), \
+               f'Booooo! Expecting a {required_type.__name__}'
+        setattr(self, variable_name, value)
+    return variable
+
+
+class Point:
+    x = check_type('x', int)
+    y = check_type('y', int)
+
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+    def move_by(self, dx, dy):
+        self.x += dx
+        self.y += dy
+
+    def __str__(self):
+        return f'A Point at {self.x}, {self.y}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.x}, {self.y})'
+
+
+class Circle:
+    center = check_type('center', Point)
+    radius = check_type('radius', int)
+
+    def __init__(self, center, radius):
+        self.center = center
+        self.radius = radius
+
+    @property
+    def area(self):
+        return pi * self.radius ** 2
+
+    def __str__(self):
+        return f'A Circle at {self.center.x}, {self.center.y} and ' + \
+               f'radius {self.radius}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.center!r}, {self.radius!r})'
+
+
+# Fewer lines of code!
+# Mind-bending?

03-property_macro_redux.py

@@ -0,0 +1,63 @@
+from math import pi
+
+
+def check_type(name, required_type):
+    variable_name = f'_{name}'
+
+    @property
+    def variable(self):
+        return getattr(self, variable_name)
+
+    @variable.setter
+    def variable(self, value):
+        assert isinstance(value, required_type), \
+               f'Booooo! Expecting a {required_type.__name__}'
+        setattr(self, variable_name, value)
+    return variable
+
+
+ensure_int = lambda name: check_type(name, int)             # noqa
+ensure_point = lambda name: check_type(name, Point)         # noqa
+
+
+class Point:
+    x = ensure_int('x')
+    y = ensure_int('y')
+
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+    def move_by(self, dx, dy):
+        self.x += dx
+        self.y += dy
+
+    def __str__(self):
+        return f'A Point at {self.x}, {self.y}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.x}, {self.y})'
+
+
+class Circle:
+    center = ensure_point('center')
+    radius = ensure_int('radius')
+
+    def __init__(self, center, radius):
+        self.center = center
+        self.radius = radius
+
+    @property
+    def area(self):
+        return pi * self.radius ** 2
+
+    def __str__(self):
+        return f'A Circle at {self.center.x}, {self.center.y} and ' + \
+               f'radius {self.radius}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.center!r}, {self.radius!r})'
+
+
+# Fewer lines of code!
+# Mind-bending?

04-descriptors.py

@@ -0,0 +1,67 @@
+from math import pi
+
+
+class TypeChecker:
+    required_type = object
+
+    def __init__(self, name):
+        self.name = name
+
+    def __get__(self, instance, owner=None):
+        return instance.__dict__[self.name]
+
+    def __set__(self, instance, value):
+        assert isinstance(value, self.required_type), \
+               f'Booooo! Expecting a {self.required_type.__name__}'
+        instance.__dict__[self.name] = value
+
+
+class IntType(TypeChecker):
+    required_type = int
+
+
+class Point:
+    x = IntType('x')
+    y = IntType('y')
+
+    def __init__(self, x, y):
+        self.x = x
+        self.y = y
+
+    def move_by(self, dx, dy):
+        self.x += dx
+        self.y += dy
+
+    def __str__(self):
+        return f'A Point at {self.x}, {self.y}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.x}, {self.y})'
+
+
+class PointType(TypeChecker):
+    required_type = Point
+
+
+class Circle:
+    center = PointType('center')
+    radius = IntType('radius')
+
+    def __init__(self, center, radius):
+        self.center = center
+        self.radius = radius
+
+    @property
+    def area(self):
+        return pi * self.radius ** 2
+
+    def __str__(self):
+        return f'A Circle at {self.center.x}, {self.center.y} and ' + \
+               f'radius {self.radius}'
+
+    def __repr__(self):
+        return f'{self.__class__.__name__}({self.center!r}, {self.radius!r})'
+
+
+# Fewer lines of code!
+# Mind-bending?