Using 'dt' as alias for datetime imports

Many well-known libraries have a conventions regarding which
alias to use. Choosing a different one will not break the code
but makes it less readable and harder to maintain for other
developers. Unless there is specific reason, it is usually best
to use the recommended alias which most people are already
familiar with. For datetime this convention is dt.

Change-Id: Ifba7b7beafdac8377b98ce952b7d3b9dade01670
Closes-Bug: #1535786

rally/plugins/openstack/scenarios/ceilometer/utils.py

@@ -12,7 +12,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import datetime
+import datetime as dt
 
 import six
 
@@ -64,7 +64,7 @@ class CeilometerScenario(scenario.OpenStackScenario):
             if v:
                 sample.update({k: v})
         len_meta = len(metadata_list) if metadata_list else 0
-        now = timestamp or datetime.datetime.utcnow()
+        now = timestamp or dt.datetime.utcnow()
         samples = []
         for i in six.moves.xrange(count):
             if i and not (i % batch_size):
@@ -72,7 +72,7 @@ class CeilometerScenario(scenario.OpenStackScenario):
                 samples = []
             sample_item = dict(sample)
             sample_item["timestamp"] = (
-                now - datetime.timedelta(seconds=(interval * i))
+                now - dt.timedelta(seconds=(interval * i))
             ).isoformat()
             if metadata_list:
                 # NOTE(idegtiarov): Adding more than one template of metadata

tests/hacking/README.rst

@@ -29,6 +29,7 @@ Rally Specific Commandments
 * [N353] - Ensure that unicode() function is not uset because of absence in py3
 * [N354] - Ensure that ``:raises: Exception`` is not used
 * [N355] - Ensure that we use only "new-style" Python classes
+* [N356] - Ensure using ``dt`` as alias for ``datetime``
 * [N360-N370] - Reserved for rules related to CLI
  * [N360] - Ensure that CLI modules do not use ``rally.common.db``
  * [N361] - Ensure that CLI modules do not use ``rally.common.objects``

tests/hacking/checks.py

@@ -64,6 +64,7 @@ re_raises = re.compile(
 re_db_import = re.compile(r"^from rally.common import db")
 re_objects_import = re.compile(r"^from rally.common import objects")
 re_old_type_class = re.compile(r"^\s*class \w+(\(\))?:")
+re_datetime_alias = re.compile(r"^(from|import) datetime(?!\s+as\s+dt$)")
 
 
 def skip_ignored_lines(func):
@@ -489,6 +490,16 @@ def check_old_type_class(logical_line, physical_line, filename):
                   "``object`` or another new-style class.")
 
 
+@skip_ignored_lines
+def check_datetime_alias(logical_line, physical_line, filename):
+    """Ensure using ``dt`` as alias for ``datetime``
+
+    N356
+    """
+    if re_datetime_alias.search(logical_line):
+        yield (0, "N356 Please use ``dt`` as alias for ``datetime``.")
+
+
 @skip_ignored_lines
 def check_db_imports_in_cli(logical_line, physical_line, filename):
     """Ensure that CLI modules do not use ``rally.common.db``
@@ -534,6 +545,7 @@ def factory(register):
     register(check_dict_formatting_in_string)
     register(check_using_unicode)
     register(check_raises)
+    register(check_datetime_alias)
     register(check_db_imports_in_cli)
     register(check_objects_imports_in_cli)
     register(check_old_type_class)

tests/unit/plugins/openstack/scenarios/ceilometer/test_utils.py

@@ -13,7 +13,7 @@
 #    under the License.
 
 import copy
-import datetime
+import datetime as dt
 
 from dateutil import parser
 import mock
@@ -33,7 +33,7 @@ class CeilometerScenarioTestCase(test.ScenarioTestCase):
     def test__make_samples_no_batch_size(self):
         self.scenario.generate_random_name = mock.Mock(
             return_value="fake_resource")
-        test_timestamp = datetime.datetime(2015, 10, 20, 14, 18, 40)
+        test_timestamp = dt.datetime(2015, 10, 20, 14, 18, 40)
         result = list(self.scenario._make_samples(count=2, interval=60,
                                                   timestamp=test_timestamp))
         self.assertEqual(1, len(result))
@@ -51,7 +51,7 @@ class CeilometerScenarioTestCase(test.ScenarioTestCase):
     def test__make_samples_batch_size(self):
         self.scenario.generate_random_name = mock.Mock(
             return_value="fake_resource")
-        test_timestamp = datetime.datetime(2015, 10, 20, 14, 18, 40)
+        test_timestamp = dt.datetime(2015, 10, 20, 14, 18, 40)
         result = list(self.scenario._make_samples(count=4, interval=60,
                                                   batch_size=2,
                                                   timestamp=test_timestamp))

tests/unit/test_hacking.py

@@ -376,3 +376,17 @@ class HackingTestCase(test.TestCase):
         checkres = checks.check_old_type_class(line, line, "fakefile")
         self.assertIsNotNone(next(checkres))
         self.assertEqual([], list(checkres))
+
+    def test_check_datetime_alias(self):
+        lines = ["import datetime as date",
+                 "import datetime",
+                 "import datetime as dto",
+                 "from datetime import datetime as dtime"]
+
+        for line in lines:
+            checkres = checks.check_datetime_alias(line, line, "fakefile")
+            self.assertIsNotNone(next(checkres))
+            self.assertEqual([], list(checkres))
+
+        line = "import datetime as dt"
+        checkres = checks.check_datetime_alias(line, line, "fakefile")