Add scalar method to RecordCollection

records.py

@@ -231,6 +231,12 @@ class RecordCollection(object):
         else:
             return record
 
+    def scalar(self, default=None):
+        """Returns the first column of the first row, or `default`."""
+        first = self.first()
+        return first[0] if first else default
+
+
 class Database(object):
     """A Database connection."""
 

tests/test_records.py

@@ -86,6 +86,24 @@ class TestRecordCollection:
         class Cheese(Exception): pass
         raises(Cheese, rows.first, Cheese('cheddar'))
 
+    # scalar
+
+    def test_scalar_returns_a_single_record(self):
+        rows = records.RecordCollection(IdRecord(i) for i in range(1))
+        assert rows.scalar() == 0
+
+    def test_scalar_defaults_to_None(self):
+        rows = records.RecordCollection(iter([]))
+        assert rows.scalar() is None
+
+    def test_scalar_default_is_overridable(self):
+        rows = records.RecordCollection(iter([]))
+        assert rows.scalar('Kaffe') == 'Kaffe'
+
+    def test_scalar_raises_when_more_than_first(self):
+        rows = records.RecordCollection(IdRecord(i) for i in range(3))
+        raises(ValueError, rows.scalar)
+
 
 class TestRecord: