Add Select.scalars(), roughly equivalent to [t[0] for t in q.tuples()]

Replaces and fixes #2611

peewee.py

@@ -2211,6 +2211,11 @@ def scalar(self, database, as_tuple=False, as_dict=False):
  row = self.tuples().peek(database)
  return row[0] if row and not as_tuple else row
 
+ @database_required
+ def scalars(self, database):
+ for row in self.tuples().execute(database):
+ yield row[0]
+
  @database_required
  def count(self, database, clear_limit=False):
  clone = self.order_by().alias('_wrapped')

tests/queries.py

@@ -116,6 +116,18 @@ def test_scalar(self):
  query = query.where(Register.value >= 2)
  self.assertEqual(query.scalar(as_tuple=True), (15, 3, 5))
 
+ def test_scalars(self):
+ values = [1.0, 1.5, 2.0, 5.0, 8.0]
+ (Register
+ .insert([{Register.value: value} for value in values])
+ .execute())
+
+ query = Register.select(Register.value).order_by(Register.value)
+ self.assertEqual(list(query.scalars()), values)
+
+ query = query.where(Register.value < 5)
+ self.assertEqual(list(query.scalars()), [1.0, 1.5, 2.0])
+
  def test_slicing_select(self):
  values = [1., 1., 2., 3., 5., 8.]
  (Register