updade from Atlas repo

25-class-metaprog/evaltime/metalib.py

@@ -0,0 +1,43 @@
+# tag::METALIB_TOP[]
+print('% metalib module start')
+
+import collections
+
+class NosyDict(collections.UserDict):
+    def __setitem__(self, key, value):
+        args = (self, key, value)
+        print(f'% NosyDict.__setitem__{args!r}')
+        super().__setitem__(key, value)
+
+    def __repr__(self):
+        return '<NosyDict instance>'
+# end::METALIB_TOP[]
+
+# tag::METALIB_BOTTOM[]
+class MetaKlass(type):
+    print('% MetaKlass body')
+
+    @classmethod  # <1>
+    def __prepare__(meta_cls, cls_name, bases):  # <2>
+        args = (meta_cls, cls_name, bases)
+        print(f'% MetaKlass.__prepare__{args!r}')
+        return NosyDict()  # <3>
+
+    def __new__(meta_cls, cls_name, bases, cls_dict):  # <4>
+        args = (meta_cls, cls_name, bases, cls_dict)
+        print(f'% MetaKlass.__new__{args!r}')
+        def inner_2(self):
+            print(f'% MetaKlass.__new__:inner_2({self!r})')
+
+        cls = super().__new__(meta_cls, cls_name, bases, cls_dict.data)  # <5>
+
+        cls.method_c = inner_2  # <6>
+
+        return cls  # <7>
+
+    def __repr__(cls):  # <8>
+        cls_name = cls.__name__
+        return f"<class {cls_name!r} built by MetaKlass>"
+
+print('% metalib module end')
+# end::METALIB_BOTTOM[]