ch17: update from book draft

17-it-generator/tree/extra/tree.py

@@ -0,0 +1,13 @@
+def tree(cls, level=0, last_in_level=True):
+    yield cls.__name__, level, last_in_level
+    subclasses = cls.__subclasses__()
+    if subclasses:
+    	last = subclasses[-1]
+    for sub_cls in subclasses:
+        yield from tree(sub_cls, level+1, sub_cls is last)
+
+
+if __name__ == '__main__':
+    for cls_name, level, _ in tree(BaseException):
+        indent = ' ' * 4 * level
+        print(f'{indent}{cls_name}')