initial

Author: fpierfed

10-interlude_dataclasses.py

@@ -0,0 +1,33 @@
+def dataclass(cls):
+    def __init__(self, *args, **kwargs):
+        for k, v in zip(cls.__annotations__.keys(), args):
+            setattr(self, k, v)
+        for k, v in kwargs.items():
+            if k not in cls.__annotations__:
+                raise TypeError(
+                    f"__init__() got an unexpected keyword argument '{k}'"
+                )
+            setattr(self, k, v)
+
+        post_init = getattr(self, '__post_init__', None)
+        if callable(post_init):
+            post_init()
+
+    def __repr__(self):
+        kwargs = {k: getattr(self, k) for k in cls.__annotations__}
+        kwstr = ', '.join([f'{k}={v}' for k, v in kwargs.items()])
+        return f'{cls.__name__}({kwstr})'
+
+    setattr(cls, '__init__', __init__)
+    setattr(cls, '__repr__', __repr__)
+    setattr(cls, '__str__', __repr__)
+    return cls
+
+
+@dataclass
+class Point:
+    x: int
+    y: int
+
+    def __post_init__(self):
+        print('  <<<Any further customizaion goes here>>>')

11-dataclasses.py

@@ -0,0 +1,55 @@
+from dataclasses import dataclass
+from math import pi
+
+
+class TypeChecker:
+    required_type = object
+
+    def __init__(self, name=None):
+        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
+
+
+def typed_dataclass(cls):
+    cls = dataclass(cls)
+
+    for var_name, var_type in cls.__annotations__.items():
+        class Checker(TypeChecker):
+            required_type = var_type
+
+        setattr(cls, var_name, Checker(var_name))
+    return cls
+
+
+@typed_dataclass
+class Point:
+    x: int
+    y: int
+
+    def move_by(self, dx, dy):
+        self.x += dx
+        self.y += dy
+
+    def __str__(self):
+        return f'A Point at {self.x}, {self.y}'
+
+
+@typed_dataclass
+class Circle:
+    center: Point
+    radius: int
+
+    @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}'

12-meta_dataclasses.py

@@ -0,0 +1,63 @@
+from dataclasses import dataclass
+from math import pi
+
+
+class TypeChecker:
+    required_type = object
+
+    def __init__(self, name=None):
+        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
+
+
+def typed_dataclass(cls):
+    cls = dataclass(cls)
+
+    for var_name, var_type in cls.__annotations__.items():
+        class Checker(TypeChecker):
+            required_type = var_type
+
+        setattr(cls, var_name, Checker(var_name))
+    return cls
+
+
+class TypeCheckMeta(type):
+    def __new__(meta, name, bases, dct):
+        cls = super().__new__(meta, name, bases, dct)
+        return typed_dataclass(cls)
+
+
+class Base(metaclass=TypeCheckMeta):
+    __annotations__ = {}
+
+
+class Point(Base):
+    x: int
+    y: int
+
+    def move_by(self, dx, dy):
+        self.x += dx
+        self.y += dy
+
+    def __str__(self):
+        return f'A Point at {self.x}, {self.y}'
+
+
+class Circle(Base):
+    center: Point
+    radius: int
+
+    @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}'