Initial commit

Exercises/soln6_3.md

@@ -0,0 +1,58 @@
+# Exercise 6.3 - Solution
+
+```python
+# structure.py
+
+import sys
+import inspect
+
+class Structure:
+    _fields = ()
+
+    @staticmethod
+    def _init():
+        locs = sys._getframe(1).f_locals
+        self = locs.pop('self')
+        for name, val in locs.items():
+            setattr(self, name, val)
+
+    def __setattr__(self, name, value):
+        if name.startswith('_') or name in self._fields:
+            super().__setattr__(name, value)
+        else:
+            raise AttributeError('No attribute %s' % name)
+
+    def __repr__(self):
+        return '%s(%s)' % (type(self).__name__,
+                           ', '.join(repr(getattr(self, name)) for name in self._fields))
+
+    @classmethod
+    def set_fields(cls):
+        sig = inspect.signature(cls)
+        cls._fields = tuple(sig.parameters)
+```
+
+Here is the `Stock` class in progress:
+
+```python
+# stock.py
+
+from structure import Structure
+
+class Stock(Structure):
+    def __init__(self, name, shares, price):
+        self._init()
+
+    @property
+    def cost(self):
+        return self.shares * self.price
+
+    def sell(self, nshares):
+        self.shares -= nshares
+
+Stock.set_fields()
+```
+
+
+
+[Back](ex6_3.md)