Decorator Patterns

Author: MilovanTomasevic

src/1_patterns/3_StructuralPatterns/4_Decorator/1_functional_decorators.py

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+import time
+
+def time_it(func):
+  def wrapper():
+    start = time.time()
+    result = func()
+    end = time.time()
+    print(f'{func.__name__} took {int((end-start)*1000)}ms')
+  return wrapper
+
+@time_it
+def some_op():
+  print('Starting op')
+  time.sleep(1)
+  print('We are done')
+  return 123
+
+if __name__ == '__main__':
+  # some_op()
+  # time_it(some_op)()
+  some_op()

src/1_patterns/3_StructuralPatterns/4_Decorator/2_oop_decorator.py

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+from abc import ABC
+
+
+class Shape(ABC):
+    def __str__(self):
+        return ''
+
+
+class Circle(Shape):
+    def __init__(self, radius=0.0):
+        self.radius = radius
+
+    def resize(self, factor):
+        self.radius *= factor
+
+    def __str__(self):
+        return f'A circle of radius {self.radius}'
+
+
+class Square(Shape):
+    def __init__(self, side):
+        self.side = side
+
+    def __str__(self):
+        return f'A square with side {self.side}'
+
+
+class ColoredShape(Shape):
+    def __init__(self, shape, color):
+        if isinstance(shape, ColoredShape):
+            raise Exception('Cannot apply ColoredDecorator twice')
+        self.shape = shape
+        self.color = color
+
+    def __str__(self):
+        return f'{self.shape} has the color {self.color}'
+
+
+class TransparentShape(Shape):
+    def __init__(self, shape, transparency):
+        self.shape = shape
+        self.transparency = transparency
+
+    def __str__(self):
+        return f'{self.shape} has {self.transparency * 100.0}% transparency'
+
+
+if __name__ == '__main__':
+    circle = Circle(2)
+    print(circle)
+
+    red_circle = ColoredShape(circle, "red")
+    print(red_circle)
+
+    # ColoredShape doesn't have resize()
+    # red_circle.resize(3)
+
+    red_half_transparent_square = TransparentShape(red_circle, 0.5)
+    print(red_half_transparent_square)
+
+    # nothing prevents double application
+    mixed = ColoredShape(ColoredShape(Circle(3), 'red'), 'blue')
+    print(mixed)

src/1_patterns/3_StructuralPatterns/4_Decorator/3_dynamic_decorator.py

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+class FileWithLogging:
+  def __init__(self, file):
+    self.file = file
+
+  def writelines(self, strings):
+    self.file.writelines(strings)
+    print(f'wrote {len(strings)} lines')
+
+  def __iter__(self):
+    return self.file.__iter__()
+
+  def __next__(self):
+    return self.file.__next__()
+
+  def __getattr__(self, item):
+    return getattr(self.__dict__['file'], item)
+
+  def __setattr__(self, key, value):
+    if key == 'file':
+      self.__dict__[key] = value
+    else:
+      setattr(self.__dict__['file'], key)
+
+  def __delattr__(self, item):
+    delattr(self.__dict__['file'], item)
+
+
+if __name__ == '__main__':
+  file = FileWithLogging(open('hello.txt', 'w'))
+  file.writelines(['hello', 'world'])
+  file.write('testing')
+  file.close()