ex 6.2

stock.py

@@ -4,6 +4,9 @@ from structure import Structure
 class Stock(Structure):
     _fields = ('name', 'shares', 'price')
 
+    def __init__(self, name, shares, price):
+        self._init()
+
     @property
     def cost(self):
         return self.shares * self.price

structure.py

@@ -1,11 +1,15 @@
+import sys
+
+
 class Structure:
     _fields = ()
 
-    def __init__(self, *args):
-        if len(args) != len(self._fields):
-            raise TypeError(f'Expected {len(self._fields)} arguments')
-        for pos, field in enumerate(self._fields):
-            setattr(self, field, args[pos])
+    @staticmethod
+    def _init():
+        locs = sys._getframe(1).f_locals
+        self = locs.pop('self')
+        for name, val in locs.items():
+            setattr(self, name, val)
 
     def __repr__(self):
         args = map(lambda field: f"{field}={getattr(self, field)!r}", self._fields)