renumbering chapters >= 19

24-class-metaprog/evaltime/builderlib.py

@@ -0,0 +1,50 @@
+# tag::BUILDERLIB_TOP[]
+print('@ builderlib module start')
+
+class Builder:  # <1>
+    print('@ Builder body')
+
+    def __init_subclass__(cls):  # <2>
+        print(f'@ Builder.__init_subclass__({cls!r})')
+
+        def inner_0(self):  # <3>
+            print(f'@ SuperA.__init_subclass__:inner_0({self!r})')
+
+        cls.method_a = inner_0
+
+    def __init__(self):
+        super().__init__()
+        print(f'@ Builder.__init__({self!r})')
+
+
+def deco(cls):  # <4>
+    print(f'@ deco({cls!r})')
+
+    def inner_1(self):  # <5>
+        print(f'@ deco:inner_1({self!r})')
+
+    cls.method_b = inner_1
+    return cls  # <6>
+# end::BUILDERLIB_TOP[]
+
+# tag::BUILDERLIB_BOTTOM[]
+class Descriptor:  # <1>
+    print('@ Descriptor body')
+
+    def __init__(self):  # <2>
+        print(f'@ Descriptor.__init__({self!r})')
+
+    def __set_name__(self, owner, name):  # <3>
+        args = (self, owner, name)
+        print(f'@ Descriptor.__set_name__{args!r}')
+
+    def __set__(self, instance, value):  # <4>
+        args = (self, instance, value)
+        print(f'@ Descriptor.__set__{args!r}')
+
+    def __repr__(self):
+        return '<Descriptor instance>'
+
+
+print('@ builderlib module end')
+# end::BUILDERLIB_BOTTOM[]

24-class-metaprog/evaltime/evaldemo.py

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+#!/usr/bin/env python3
+
+from builderlib import Builder, deco, Descriptor
+
+print('# evaldemo module start')
+
+@deco  # <1>
+class Klass(Builder):  # <2>
+    print('# Klass body')
+
+    attr = Descriptor()  # <3>
+
+    def __init__(self):
+        super().__init__()
+        print(f'# Klass.__init__({self!r})')
+
+    def __repr__(self):
+        return '<Klass instance>'
+
+
+def main():  # <4>
+    obj = Klass()
+    obj.method_a()
+    obj.method_b()
+    obj.attr = 999
+
+if __name__ == '__main__':
+    main()
+
+print('# evaldemo module end')

24-class-metaprog/evaltime/evaldemo_meta.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+
+from builderlib import Builder, deco, Descriptor
+from metalib import MetaKlass  # <1>
+
+print('# evaldemo_meta module start')
+
+@deco
+class Klass(Builder, metaclass=MetaKlass):  # <2>
+    print('# Klass body')
+
+    attr = Descriptor()
+
+    def __init__(self):
+        super().__init__()
+        print(f'# Klass.__init__({self!r})')
+
+    def __repr__(self):
+        return '<Klass instance>'
+
+
+def main():
+    obj = Klass()
+    obj.method_a()
+    obj.method_b()
+    obj.method_c()  # <3>
+    obj.attr = 999
+
+
+if __name__ == '__main__':
+    main()
+
+print('# evaldemo_meta module end')

24-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[]