ex5.4

typedproperty.py

@@ -0,0 +1,41 @@
+def typedproperty(name, expected_type):
+    private_name = "_" + name
+
+    @property
+    def value(self):
+        return getattr(self, private_name)
+
+    @value.setter
+    def value(self, val):
+        if not isinstance(val, expected_type):
+            raise TypeError(f"Expected {expected_type}")
+        setattr(self, private_name, val)
+
+    return value
+
+
+def String(name):
+    return typedproperty(name, str)
+
+
+def Integer(name):
+    return typedproperty(name, int)
+
+
+def Float(name):
+    return typedproperty(name, float)
+
+
+if __name__ == "__main__":
+
+    class Stock:
+        name = String("name")
+        shares = Integer("shares")
+        price = Float("price")
+
+        def __init__(self, name, shares, price):
+            self.name = name
+            self.shares = shares
+            self.price = price
+
+    print(Stock)