ex 3.3

reader.py

@@ -37,8 +37,8 @@ def read_csv_as_dicts(filename, conversions):
         headers = next(rows)
         for row in rows:
             value.append(
-                {name: func(val)
+                {name: func(val) for name, func, val in zip(headers, conversions, row)}
-                 for name, func, val in zip(headers, conversions, row)})
+            )
     return value
 
 
@@ -49,6 +49,17 @@ def read_csv_as_columns(filename, conversions):
         value = DataCollection(headers)
         for row in rows:
             value.append(
-                {name: func(val)
+                {name: func(val) for name, func, val in zip(headers, conversions, row)}
-                 for name, func, val in zip(headers, conversions, row)})
+            )
     return value
+
+
+def read_csv_as_instances(filename, cls):
+    """Read a CSV file into a list of instances"""
+    records = []
+    with open(filename) as f:
+        rows = csv.reader(f)
+        _ = next(rows)
+        for row in rows:
+            records.append(cls.from_row(row))
+    return records

stock.py

@@ -1,12 +1,21 @@
 import csv
 
+from Decimal import Decimal
+
 
 class Stock:
+    types = (str, int, float)
+
     def __init__(self, name, shares, price):
         self.name = name
         self.shares = shares
         self.price = price
 
+    @classmethod
+    def from_row(cls, row):
+        values = [func(val) for func, val in zip(cls.types, row)]
+        return cls(*values)
+
     def cost(self):
         return self.shares * self.price
 
@@ -16,13 +25,6 @@ class Stock:
             self.shares = 0
 
 
-def read_portfolio(filename):
-    with open(filename) as f:
-        rows = csv.reader(f)
-        _ = next(rows)
-        return [Stock(row[0], row[1], row[2]) for row in rows]
-
-
 def print_portfolio(portfolio):
     headers = ("name", "shares", "price")
     fmtstr = "{0: >10} {1: >10} {2: >10}"