diff --git a/tests/scripts/thread-cert/node.py b/tests/scripts/thread-cert/node.py
index 62a1e7f5f..aee76b7e9 100755
--- a/tests/scripts/thread-cert/node.py
+++ b/tests/scripts/thread-cert/node.py
@@ -67,9 +67,9 @@ class Node:
 
     def __init_sim(self, nodeid, mode):
         """ Initialize a simulation node. """
-        if 'OT_CLI_PATH' in os.environ.keys():
+        if 'OT_CLI_PATH' in os.environ:
             cmd = os.environ['OT_CLI_PATH']
-        elif 'top_builddir' in os.environ.keys():
+        elif 'top_builddir' in os.environ:
             srcdir = os.environ['top_builddir']
             cmd = '%s/examples/apps/cli/ot-cli-%s' % (srcdir, mode)
         else:
@@ -102,12 +102,12 @@ class Node:
         else:
             args = ''
 
-        if 'OT_NCP_PATH' in os.environ.keys():
+        if 'OT_NCP_PATH' in os.environ:
             cmd = 'spinel-cli.py -p "%s%s" -n' % (
                 os.environ['OT_NCP_PATH'],
                 args,
             )
-        elif "top_builddir" in os.environ.keys():
+        elif "top_builddir" in os.environ:
             builddir = os.environ['top_builddir']
             cmd = 'spinel-cli.py -p "%s/examples/apps/ncp/ot-ncp-%s%s" -n' % (
                 builddir,
diff --git a/tests/scripts/thread-cert/test_route_table.py b/tests/scripts/thread-cert/test_route_table.py
index 2f38e7d2f..5ad519adc 100755
--- a/tests/scripts/thread-cert/test_route_table.py
+++ b/tests/scripts/thread-cert/test_route_table.py
@@ -93,7 +93,7 @@ class TestRouteTable(unittest.TestCase):
 
         for _node in self.nodes.values():
             router_table = _node.router_table()
-            self.assertEqual(set(router_table.keys()), router_ids)
+            self.assertEqual(set(router_table), router_ids)
 
 
 if __name__ == '__main__':
diff --git a/tools/harness-automation/autothreadharness/runner.py b/tools/harness-automation/autothreadharness/runner.py
index 6950f3d1f..c748894c2 100644
--- a/tools/harness-automation/autothreadharness/runner.py
+++ b/tools/harness-automation/autothreadharness/runner.py
@@ -285,7 +285,7 @@ def discover(
                     continue
 
                 # skip cases
-                if case_name in log.keys():
+                if case_name in log:
                     if ((log[case_name]['passed'] and ('p' in skip)) or
                         (log[case_name]['passed'] is False and ('f' in skip)) or
                         (log[case_name]['passed'] is None and ('e' in skip))):