Ex 7.1

logcall.py

@@ -0,0 +1,6 @@
+def logged(func):
+    print('Adding logging to', func.__name__)
+    def wrapper(*args, **kwargs):
+        print('Calling', func.__name__)
+        return func(*args, **kwargs)
+    return wrapper

sample.py

@@ -0,0 +1,11 @@
+from logcall import logged
+
+
+@logged
+def add(x, y):
+    return x + y
+
+
+@logged
+def sub(x, y):
+    return x - y

validate.py

@@ -66,6 +66,31 @@ class NonEmptyString(String, NonEmpty):
     pass
 
 
+def validated(func):
+    sig = inspect.signature(func)
+    annotations = dict(func.__annotations__)
+    retcheck = annotations.pop('return', None)
+
+    def wrapper(*args, **kwargs):
+        bound = sig.bind(*args, **kwargs)
+        errors = []
+        for name, validator in annotations.items():
+            try:
+                validator.check(bound.arguments[name])
+            except Exception as e:
+                errors.append(f'   {name}: {e}')
+        if errors:
+            raise TypeError('Bad Arguments\n' + '\n'.join(errors))
+        result = func(*args, **kwargs)
+        if retcheck:
+            try:
+                retcheck.check(result)
+            except Exception as e:
+                raise TypeError(f'Bad return: {e}') from None
+        return result
+    return wrapper
+
+
 class ValidatedFunction:
     def __init__(self, func):
         self.func = func
@@ -83,6 +108,10 @@ class ValidatedFunction:
 
 
 if __name__ == '__main__':
+    @validated
     def add(x: Integer, y: Integer):
         return x + y
-    add = ValidatedFunction(add)
+
+    @validated
+    def power(x: Integer, y: Integer):
+        return x ** y