Use sequence directly instead of using len()

This commit makes to use sequence directly instead of using
len(SEQUENCE). The original code works correctly, and it's really
straight forward. However, PEP8 recommends like below[1]. And it
makes code more simple, too.

```
For sequences, (strings, lists, tuples), use the fact that empty
sequences are false.

Yes: if not seq:
     if seq:

No: if len(seq):
    if not len(seq):
```

[1] https://www.python.org/dev/peps/pep-0008/#programming-recommendations

Change-Id: I8d41e16d82b1b3860a98e5217cb7a541fc83b907

tempest/api/compute/admin/test_hypervisor.py

@@ -104,7 +104,7 @@ class HypervisorAdminTestJSON(base.BaseV2ComputeAdminTest):
             try:
                 uptime = (self.client.show_hypervisor_uptime(hyper['id'])
                           ['hypervisor'])
-                if len(uptime) > 0:
+                if uptime:
                     has_valid_uptime = True
                     break
             except Exception:

tempest/api/compute/servers/test_novnc.py

@@ -82,7 +82,7 @@ class NoVNCConsoleTestJSON(base.BaseV2ComputeTest):
         """Verify we can connect to novnc and do the websocket connection."""
         # Turn the Socket into a WebSocket to do the communication
         data = self._websocket.receive_frame()
-        self.assertFalse(data is None or len(data) == 0,
+        self.assertFalse(data is None or not data,
                          'Token must be invalid because the connection '
                          'closed.')
         # Parse the RFB version from the data to make sure it is valid
@@ -181,6 +181,6 @@ class NoVNCConsoleTestJSON(base.BaseV2ComputeTest):
         self._websocket = compute.create_websocket(url)
         # Make sure the novncproxy rejected the connection and closed it
         data = self._websocket.receive_frame()
-        self.assertTrue(data is None or len(data) == 0,
+        self.assertTrue(data is None or not data,
                         "The novnc proxy actually sent us some data, but we "
                         "expected it to close the connection.")

tempest/api/compute/test_extensions.py

@@ -31,7 +31,7 @@ class ExtensionsTestJSON(base.BaseV2ComputeTest):
     @decorators.idempotent_id('3bb27738-b759-4e0d-a5fa-37d7a6df07d1')
     def test_list_extensions(self):
         # List of all extensions
-        if len(CONF.compute_feature_enabled.api_extensions) == 0:
+        if not CONF.compute_feature_enabled.api_extensions:
             raise self.skipException('There are not any extensions configured')
         extensions = self.extensions_client.list_extensions()['extensions']
         ext = CONF.compute_feature_enabled.api_extensions[0]

tempest/api/identity/base.py

@@ -47,7 +47,7 @@ class BaseIdentityTest(tempest.test.BaseTestCase):
         else:
             users = cls.users_client.list_users()['users']
         user = [u for u in users if u['name'] == name]
-        if len(user) > 0:
+        if user:
             return user[0]
 
     @classmethod
@@ -57,14 +57,14 @@ class BaseIdentityTest(tempest.test.BaseTestCase):
         except AttributeError:
             tenants = cls.projects_client.list_projects()['projects']
         tenant = [t for t in tenants if t['name'] == name]
-        if len(tenant) > 0:
+        if tenant:
             return tenant[0]
 
     @classmethod
     def get_role_by_name(cls, name):
         roles = cls.roles_client.list_roles()['roles']
         role = [r for r in roles if r['name'] == name]
-        if len(role) > 0:
+        if role:
             return role[0]
 
     def create_test_user(self, **kwargs):

tempest/api/network/base.py

@@ -106,7 +106,7 @@ class BaseNetworkTest(tempest.test.BaseTestCase):
 
             # Clean up metering label rules
             # Not all classes in the hierarchy have the client class variable
-            if len(cls.metering_label_rules) > 0:
+            if cls.metering_label_rules:
                 label_rules_client = cls.admin_metering_label_rules_client
                 for metering_label_rule in cls.metering_label_rules:
                     test_utils.call_and_ignore_notfound_exc(

tempest/api/volume/test_extensions.py

@@ -32,7 +32,7 @@ class ExtensionsTestJSON(base.BaseVolumeTest):
         # List of all extensions
         extensions = (self.volumes_extension_client.list_extensions()
                       ['extensions'])
-        if len(CONF.volume_feature_enabled.api_extensions) == 0:
+        if not CONF.volume_feature_enabled.api_extensions:
             raise self.skipException('There are not any extensions configured')
         extension_list = [extension.get('alias') for extension in extensions]
         LOG.debug("Cinder extensions: %s", ','.join(extension_list))

tempest/api/volume/test_volumes_list.py

@@ -47,7 +47,7 @@ class VolumesListTestJSON(base.BaseVolumeTest):
             fetched_list = [fieldsgetter(item) for item in fetched_list]
 
         missing_vols = [v for v in expected_list if v not in fetched_list]
-        if len(missing_vols) == 0:
+        if not missing_vols:
             return
 
         def str_vol(vol):

tempest/cmd/cleanup_service.py

@@ -105,7 +105,7 @@ class BaseService(object):
 
     def _filter_by_tenant_id(self, item_list):
         if (item_list is None
-                or len(item_list) == 0
+                or not item_list
                 or not hasattr(self, 'tenant_id')
                 or self.tenant_id is None
                 or 'tenant_id' not in item_list[0]):

tempest/common/compute.py

@@ -258,7 +258,7 @@ class _WebSocket(object):
         while True:
             header = self._socket.recv(2)
             # If we didn't receive any data, just return None
-            if len(header) == 0:
+            if not header:
                 return None
             # We will make the assumption that we are only dealing with
             # frames less than 125 bytes here (for the negotiation) and
@@ -313,6 +313,6 @@ class _WebSocket(object):
         self._socket.sendall(reqdata.encode('utf8'))
         self.response = data = self._socket.recv(4096)
         # Loop through & concatenate all of the data in the response body
-        while len(data) > 0 and self.response.find(b'\r\n\r\n') < 0:
+        while data and self.response.find(b'\r\n\r\n') < 0:
             data = self._socket.recv(4096)
             self.response += data

tempest/common/preprov_creds.py

@@ -241,7 +241,7 @@ class PreProvisionedCredentialProvider(cred_provider.CredentialProvider):
 
     def _get_creds(self, roles=None):
         useable_hashes = self._get_match_hash_list(roles)
-        if len(useable_hashes) == 0:
+        if not useable_hashes:
             msg = 'No users configured for type/roles %s' % roles
             raise lib_exc.InvalidCredentials(msg)
         free_hash = self._get_free_hash(useable_hashes)

tempest/lib/auth.py

@@ -539,18 +539,18 @@ class KeystoneV3AuthProvider(KeystoneAuthProvider):
 
         # Select entries with matching service type
         service_catalog = [ep for ep in catalog if ep['type'] == service]
-        if len(service_catalog) > 0:
+        if service_catalog:
             if name is not None:
                 service_catalog = (
                     [ep for ep in service_catalog if ep['name'] == name])
-                if len(service_catalog) > 0:
+                if service_catalog:
                     service_catalog = service_catalog[0]['endpoints']
                 else:
                     raise exceptions.EndpointNotFound(name)
             else:
                 service_catalog = service_catalog[0]['endpoints']
         else:
-            if len(catalog) == 0 and service == 'identity':
+            if not catalog and service == 'identity':
                 # NOTE(andreaf) If there's no catalog at all and the service
                 # is identity, it's a valid use case. Having a non-empty
                 # catalog with no identity in it is not valid instead.
@@ -571,13 +571,13 @@ class KeystoneV3AuthProvider(KeystoneAuthProvider):
         # Filter by endpoint type (interface)
         filtered_catalog = [ep for ep in service_catalog if
                             ep['interface'] == endpoint_type]
-        if len(filtered_catalog) == 0:
+        if not filtered_catalog:
             # No matching type, keep all and try matching by region at least
             filtered_catalog = service_catalog
         # Filter by region
         filtered_catalog = [ep for ep in filtered_catalog if
                             ep['region'] == region]
-        if len(filtered_catalog) == 0:
+        if not filtered_catalog:
             # No matching region (or name), take the first endpoint
             filtered_catalog = [service_catalog[0]]
         # There should be only one match. If not take the first.

tempest/lib/cli/output_parser.py

@@ -114,7 +114,7 @@ def tables(output_lines):
                 label = line
             else:
                 LOG.warning('Invalid line between tables: %s', line)
-    if len(table_) > 0:
+    if table_:
         LOG.warning('Missing end of table')
 
     return tables_

tempest/lib/exceptions.py

@@ -32,7 +32,7 @@ class TempestException(Exception):
         except Exception:
             # at least get the core message out if something happened
             self._error_string = self.message
-        if len(args) > 0:
+        if args:
             # If there is a non-kwarg parameter, assume it's the error
             # message or reason description and tack it on to the end
             # of the exception message

tempest/lib/services/image/v1/images_client.py

@@ -118,7 +118,7 @@ class ImagesClient(rest_client.RestClient):
         if 'changes_since' in kwargs:
             kwargs['changes-since'] = kwargs.pop('changes_since')
 
-        if len(kwargs) > 0:
+        if kwargs:
             url += '?%s' % urllib.urlencode(kwargs)
 
         resp, body = self.get(url)

tempest/test.py

@@ -139,7 +139,7 @@ def is_extension_enabled(extension_name, service):
         'object': CONF.object_storage_feature_enabled.discoverable_apis,
         'identity': CONF.identity_feature_enabled.api_extensions
     }
-    if len(config_dict[service]) == 0:
+    if not config_dict[service]:
         return False
     if config_dict[service][0] == 'all':
         return True
@@ -160,7 +160,7 @@ def is_scheduler_filter_enabled(filter_name):
     """
 
     filters = CONF.compute_feature_enabled.scheduler_available_filters
-    if len(filters) == 0:
+    if not filters:
         return False
     if 'all' in filters:
         return True
@@ -634,7 +634,7 @@ class BaseTestCase(testtools.testcase.WithAttributes,
         """
         if msg is None:
             msg = "sequence or collection is not empty: %s" % items
-        self.assertEqual(0, len(items), msg)
+        self.assertFalse(items, msg)
 
     def assertNotEmpty(self, items, msg=None):
         """Asserts whether a sequence or collection is not empty
@@ -645,4 +645,4 @@ class BaseTestCase(testtools.testcase.WithAttributes,
         """
         if msg is None:
             msg = "sequence or collection is empty."
-        self.assertGreater(len(items), 0, msg)
+        self.assertTrue(items, msg)