Step 1: Source and Decorator base

The Decorator pattern lets you wrap an object in another object that has the same interface, adding behavior on the way through. Real stream libraries do exactly this: a GzipStream wraps a FileStream, a Base64Stream wraps that, and to the caller they all just look like something with a read() method.

We start with two building blocks.

Source already holds some text and returns it from read(). Nothing to do there.
Decorator wraps another object (its wrapped attribute) and must expose the same read() interface. The base decorator is transparent: it simply forwards the call to the thing it wraps and returns the result unchanged.

Implement Decorator.read so a bare Decorator behaves identically to the source it wraps. This delegation is the backbone every later transformer builds on.

Hints

class Source: def __init__(self, text): self.text = text def read(self): return self.text class Decorator: def __init__(self, wrapped): self.wrapped = wrapped def read(self): """Delegate to the wrapped source, returning its read() unchanged.""" # TODO: # return self.wrapped.read() pass

Step 1: Source and Decorator base

We start with two building blocks.

Source already holds some text and returns it from read(). Nothing to do there.

Decorator wraps another object (its wrapped attribute) and must expose the same read() interface. The base decorator is transparent: it simply forwards the call to the thing it wraps and returns the result unchanged.

Implement Decorator.read so a bare Decorator behaves identically to the source it wraps. This delegation is the backbone every later transformer builds on.

Hints