Initial commit

Solutions/5_2/reader.py

@@ -0,0 +1,49 @@
+# reader.py
+
+from abc import ABC, abstractmethod
+import csv
+import logging
+log = logging.getLogger(__name__)
+
+class CSVParser(ABC):
+
+    def parse(self, filename):
+        records = []
+        with open(filename) as f:
+            rows = csv.reader(f)
+            headers = next(rows)
+            for rowno, row in enumerate(rows, start=1):
+                try:
+                    record = self.make_record(headers, row)
+                    records.append(record)
+                except ValueError as e:
+                    log.warning('Row %d: Bad row: %s', rowno, row)
+                    log.debug('Row %d: Reason: %s', rowno, e)
+
+        return records
+
+    @abstractmethod
+    def make_record(self, headers, row):
+        raise NotImplementedError()
+
+class DictCSVParser(CSVParser):
+    def __init__(self, types):
+        self.types = types
+
+    def make_record(self, headers, row):
+        return { name: func(val) for name, func, val in zip(headers, self.types, row) }
+
+class InstanceCSVParser(CSVParser):
+    def __init__(self, cls):
+        self.cls = cls
+
+    def make_record(self, headers, row):
+        return self.cls.from_row(row)
+
+def read_csv_as_dicts(filename, types):
+    parser = DictCSVParser(types)
+    return parser.parse(filename)
+
+def read_csv_as_instances(filename, cls):
+    parser = InstanceCSVParser(cls)
+    return parser.parse(filename)

Solutions/5_2/stock.py

@@ -0,0 +1,51 @@
+# stock.py
+
+class Stock:
+    __slots__ = ('name','_shares','_price')
+    _types = (str, int, float)
+    def __init__(self, name, shares, price):
+        self.name = name
+        self.shares = shares
+        self.price = price
+
+    def __repr__(self):
+        # Note: The !r format code produces the repr() string
+        return f'{type(self).__name__}({self.name!r}, {self.shares!r}, {self.price!r})'
+
+    def __eq__(self, other):
+        return isinstance(other, Stock) and ((self.name, self.shares, self.price) ==
+                (other.name, other.shares, other.price))
+
+    @classmethod
+    def from_row(cls, row):
+        values = [func(val) for func, val in zip(cls._types, row)]
+        return cls(*values)
+
+    @property
+    def shares(self):
+        return self._shares
+    @shares.setter
+    def shares(self, value):
+        if not isinstance(value, self._types[1]):
+            raise TypeError(f'Expected {self._types[1].__name__}')
+        if value < 0:
+            raise ValueError('shares must be >= 0')
+        self._shares = value
+
+    @property
+    def price(self):
+        return self._price
+    @price.setter
+    def price(self, value):
+        if not isinstance(value, self._types[2]):
+            raise TypeError(f'Expected {self._types[2].__name__}')
+        if value < 0:
+            raise ValueError('price must be >= 0')
+        self._price = value
+
+    @property
+    def cost(self):
+        return self.shares * self.price
+
+    def sell(self, nshares):
+        self.shares -= nshares