@@ -3,44 +3,43 @@
 # Exercise 3.3
 import csv
 
-def parse_csv(filename, select=None, types=None, has_headers=True, delimiter=',', silence_errors=True):
+def parse_csv(file_obj, select=None, types=None, has_headers=True, delimiter=',', silence_errors=True):
     '''
     Parse a CSV file into a list of records
     '''
-    with open(filename) as f:
-        rows = csv.reader(f, delimiter=delimiter)
+    rows = csv.reader(file_obj, delimiter=delimiter)
 
-        if select and not has_headers:
-            raise RuntimeError('select argument requires column headers')
+    if select and not has_headers:
+        raise RuntimeError('select argument requires column headers')
 
-        #Read headers
+    #Read headers
+    if has_headers:
+        headers = next(rows)
+    
+    if select:
+        indeces = [headers.index(colname) for colname in select]
         if has_headers:
-            headers = next(rows)
-        
-        if select:
-            indeces = [headers.index(colname) for colname in select]
-            if has_headers:
-                headers = select
-        else:
-            indeces = []
+            headers = select
+    else:
+        indeces = []
 
-        records = []
-        for rowNum, row in enumerate(rows, start=1):
-            if not row: #skip empty rows
-                continue
-            
-            try:
-                if indeces:
-                    row = [row[index] for index in indeces]
-                if types:
-                    row = [func(val) for func, val in zip(types, row)]
+    records = []
+    for rowNum, row in enumerate(rows, start=1):
+        if not row: #skip empty rows
+            continue
+        
+        try:
+            if indeces:
+                row = [row[index] for index in indeces]
+            if types:
+                row = [func(val) for func, val in zip(types, row)]
 
-                if has_headers:
-                    records.append({name: value for name, value in zip(headers,row)})
-                else:
-                    records.append(row)
-            except ValueError as ve:
-                if not silence_errors:
-                    print(f'Row {rowNum}: Couldn\'t convert {row}')
-                    print(f'Row {rowNum}: Reason {ve}')
+            if has_headers:
+                records.append({name: value for name, value in zip(headers,row)})
+            else:
+                records.append(row)
+        except ValueError as ve:
+            if not silence_errors:
+                print(f'Row {rowNum}: Couldn\'t convert {row}')
+                print(f'Row {rowNum}: Reason {ve}')
     return records
@@ -14,14 +14,17 @@
 
 def read_portfolio(filename):
     select=['name', 'shares', 'price']
-    portfolio = parse_csv(filename, select=select, 
-        types=[types_headers[type_name] for type_name in select])
+    with open(filename) as f:
+        portfolio = parse_csv(f, select=select, 
+            types=[types_headers[type_name] for type_name in select])
 
     return portfolio
 
 def read_prices(filename):
     'reads set of stock prices from filename and returns a dictionary'
-    price_tuples = parse_csv(filename, types=[str, float], has_headers=False)
+    with open(filename) as f:
+        price_tuples = parse_csv(f, types=[str, float], has_headers=False)
+    
     prices = {tup[0] : tup[1] for tup in price_tuples}
 
     return prices