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Exercises/soln6_1.md

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+# Exercise 6.1 - Solution
+
+## (a) Simplified Structures
+
+```python
+# structure.py
+
+class Structure:
+    _fields = ()
+    def __init__(self, *args):
+        if len(args) != len(self._fields):
+            raise TypeError('Expected %d arguments' % len(self._fields))
+        for name, arg in zip(self._fields,args):
+            setattr(self, name, arg)
+```
+
+## (b) Making a Useful Representation
+
+[source, python]
+```
+class Structure:
+    ...    
+    def __repr__(self):
+        return '%s(%s)' % (type(self).__name__,
+                           ', '.join(repr(getattr(self, name)) for name in self._fields))
+```
+
+## (c) Restricting Attribute Names
+
+[source, python]
+```
+class Structure:
+    ...    
+    def __setattr__(self, name, value):
+        if name.startswith('_') or name in self._fields:
+            super().__setattr__(name, value)
+        else:
+            raise AttributeError('No attribute %s' % name)
+```
+
+
+
+[Back](ex6_1.md)