Initial commit

Solutions/6_4/stock.py

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+# stock.py
+
+from structure import Structure
+
+class Stock(Structure):
+    _fields = ('name', 'shares', 'price')
+
+    @property
+    def cost(self):
+        return self.shares * self.price
+
+    def sell(self, nshares):
+        self.shares -= nshares
+
+Stock.create_init()
+

Solutions/6_4/structure.py

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+# structure.py
+
+class Structure:
+    _fields = ()
+
+    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 create_init(cls):
+        '''
+        Create an __init__ method from _fields
+        '''
+        args = ','.join(cls._fields)
+        code = f'def __init__(self, {args}):\n'
+        for name in cls._fields:
+            code += f'    self.{name} = {name}\n'
+        locs = { }
+        exec(code, locs)
+        cls.__init__ = locs['__init__']

Solutions/6_4/teststock.py

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+# teststock.py
+
+import stock
+import unittest
+
+class TestStock(unittest.TestCase):
+    def test_create(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        self.assertEqual(s.name, 'GOOG')
+        self.assertEqual(s.shares, 100)
+        self.assertEqual(s.price, 490.1)
+
+    def test_create_keyword(self):
+        s = stock.Stock(name='GOOG', shares=100, price=490.1)
+        self.assertEqual(s.name, 'GOOG')
+        self.assertEqual(s.shares, 100)
+        self.assertEqual(s.price, 490.1)
+        
+    def test_cost(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        self.assertEqual(s.cost, 49010.0)
+
+    def test_sell(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        s.sell(25)
+        self.assertEqual(s.shares, 75)
+
+    def test_from_row(self):
+        s = stock.Stock.from_row(['GOOG','100','490.1'])
+        self.assertEqual(s.name, 'GOOG')
+        self.assertEqual(s.shares, 100)
+        self.assertEqual(s.price, 490.1)
+
+    def test_repr(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        self.assertEqual(repr(s), "Stock('GOOG', 100, 490.1)")
+
+    def test_eq(self):
+        a = stock.Stock('GOOG', 100, 490.1)
+        b = stock.Stock('GOOG', 100, 490.1)
+        self.assertTrue(a==b)
+
+    # Tests for failure conditions
+    def test_shares_badtype(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        with self.assertRaises(TypeError):
+            s.shares = '50'
+
+    def test_shares_badvalue(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        with self.assertRaises(ValueError):
+            s.shares = -50
+
+    def test_price_badtype(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        with self.assertRaises(TypeError):
+            s.price = '45.23'
+
+    def test_price_badvalue(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        with self.assertRaises(ValueError):
+            s.price = -45.23
+
+    def test_bad_attribute(self):
+        s = stock.Stock('GOOG', 100, 490.1)
+        with self.assertRaises(AttributeError):
+            s.share = 100
+
+if __name__ == '__main__':
+    unittest.main()