Better fix for #2871, fixes #2872.

peewee.py

@@ -2095,7 +2095,7 @@ def iterator(self, database=None):
         return iter(self.execute(database).iterator())
 
     def _ensure_execution(self):
-        if not self._cursor_wrapper:
+        if self._cursor_wrapper is None:
             if not self._database:
                 raise ValueError('Query has not been executed.')
             self.execute()
@@ -4572,9 +4572,6 @@ def __len__(self):
         self.fill_cache()
         return self.count
 
-    def __bool__(self):
-        return self.populated
-
     def initialize(self):
         pass
 

tests/regressions.py

@@ -1801,3 +1801,13 @@ def run(n):
                    for i in (0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.5)]
         for t in threads: t.start()
         for t in threads: t.join()
+
+
+class TestQueryCountList(ModelTestCase):
+    requires = [User]
+
+    def test_iteration_single_query(self):
+        with self.assertQueryCount(1):
+            list(User.select())
+        with self.assertQueryCount(1):
+            self.assertEqual(User.select().count(), 0)