Adding a data writer module

ingredient_phrase_tagger/training/labelled_data.py

@@ -74,3 +74,28 @@ def _parse_row(row):
         'unit': row['unit'].decode('utf-8'),
         'comment': row['comment'].decode('utf-8'),
     }
+
+
+class Writer(object):
+    """Writes labelled ingredient data to a CSV file."""
+
+    def __init__(self, data_file):
+        self._csv_writer = csv.DictWriter(
+            data_file, fieldnames=_REQUIRED_COLUMNS, lineterminator='\n')
+        self._csv_writer.writeheader()
+
+    def writerow(self, row):
+        """Adds a row of data to the output CSV file.
+
+        Args:
+            row: A dictionary of values for a labelled ingredient. The
+                dictionary must contain the following keys:
+
+                * input
+                * name
+                * qty
+                * range_end
+                * unit
+                * comment
+        """
+        self._csv_writer.writerow(row)

tests/test_labelled_data.py

@@ -65,3 +65,50 @@ def test_raises_error_when_csv_does_not_have_required_columns(self):
 77,3 bananas,bananas,3.0,0.0,,
 """.strip())
             labelled_data.Reader(mock_file).next()
+
+
+class WriterTest(unittest.TestCase):
+
+    def setUp(self):
+        self.maxDiff = None
+
+    def test_writes_valid_rows(self):
+        mock_file = io.BytesIO()
+        writer = labelled_data.Writer(mock_file)
+        mock_rows = [{
+            'input': u'4 to 6 large cloves garlic',
+            'qty': 4.0,
+            'unit': u'clove',
+            'name': u'garlic',
+            'range_end': 6.0,
+            'comment': u'',
+        }, {
+            'input': u'3 bananas',
+            'qty': 3.0,
+            'unit': u'',
+            'name': u'bananas',
+            'comment': u'',
+            'range_end': 0.0,
+        }, {
+            'input': (u'2 1/2 pounds bell peppers (about 6 peppers in '
+                      u'assorted colors), cut into 2-inch chunks'),
+            'qty':
+            2.5,
+            'unit':
+            u'pound',
+            'name':
+            u'bell peppers',
+            'range_end':
+            0.0,
+            'comment': (u'(about 6 peppers in assorted colors), cut into '
+                        u'2-inch chunks'),
+        }]
+        for row in mock_rows:
+            writer.writerow(row)
+        self.assertMultiLineEqual("""
+input,name,qty,range_end,unit,comment
+4 to 6 large cloves garlic,garlic,4.0,6.0,clove,
+3 bananas,bananas,3.0,0.0,,
+"2 1/2 pounds bell peppers (about 6 peppers in assorted colors), cut into 2-inch chunks",bell peppers,2.5,0.0,pound,"(about 6 peppers in assorted colors), cut into 2-inch chunks"
+""".strip(),
+                                  mock_file.getvalue().strip())