diff --git a/android/pylib/base/base_test_result_unittest.py b/android/pylib/base/base_test_result_unittest.py
index f038b3199..591b8f386 100644
--- a/android/pylib/base/base_test_result_unittest.py
+++ b/android/pylib/base/base_test_result_unittest.py
@@ -6,9 +6,9 @@
 
 import unittest
 
-from base_test_result import BaseTestResult
-from base_test_result import TestRunResults
-from base_test_result import ResultType
+from pylib.base.base_test_result import BaseTestResult
+from pylib.base.base_test_result import TestRunResults
+from pylib.base.base_test_result import ResultType
 
 
 class TestTestRunResults(unittest.TestCase):
diff --git a/android/pylib/base/base_test_runner.py b/android/pylib/base/base_test_runner.py
index 2688a6fbf..44a457bff 100644
--- a/android/pylib/base/base_test_runner.py
+++ b/android/pylib/base/base_test_runner.py
@@ -4,15 +4,10 @@
 
 """Base class for running tests on a single device."""
 
-import contextlib
-import httplib
 import logging
-import os
-import tempfile
 import time
 
 from pylib import android_commands
-from pylib import constants
 from pylib import ports
 from pylib.chrome_test_server_spawner import SpawningServer
 from pylib.forwarder import Forwarder
@@ -181,7 +176,7 @@ class BaseTestRunner(object):
     # well as IsHttpServerConnectable(). spawning_server.Start() should also
     # block until the server is ready.
     # Try 3 times to launch test spawner server.
-    for i in xrange(0, 3):
+    for _ in xrange(0, 3):
       self.test_server_spawner_port = ports.AllocateTestServerPort()
       self._ForwardPorts(
           [(self.test_server_spawner_port, self.test_server_spawner_port)])
diff --git a/android/pylib/base/test_dispatcher.py b/android/pylib/base/test_dispatcher.py
index 11374bbf4..5f68a7ff4 100644
--- a/android/pylib/base/test_dispatcher.py
+++ b/android/pylib/base/test_dispatcher.py
@@ -20,11 +20,10 @@ import threading
 
 from pylib import android_commands
 from pylib import constants
+from pylib.base import base_test_result
 from pylib.utils import reraiser_thread
 from pylib.utils import watchdog_timer
 
-import base_test_result
-
 
 DEFAULT_TIMEOUT = 7 * 60  # seven minutes
 
@@ -69,7 +68,9 @@ class _TestCollection(object):
     tests: List of tests to put in the collection.
   """
 
-  def __init__(self, tests=[]):
+  def __init__(self, tests=None):
+    if not tests:
+      tests = []
     self._lock = threading.Lock()
     self._tests = []
     self._tests_in_progress = 0
diff --git a/android/pylib/base/test_dispatcher_unittest.py b/android/pylib/base/test_dispatcher_unittest.py
index c6078dbdf..1409b5bbc 100644
--- a/android/pylib/base/test_dispatcher_unittest.py
+++ b/android/pylib/base/test_dispatcher_unittest.py
@@ -3,6 +3,8 @@
 # found in the LICENSE file.
 
 """Unittests for test_dispatcher.py."""
+# pylint: disable=R0201
+# pylint: disable=W0212
 
 import os
 import sys
@@ -15,10 +17,10 @@ sys.path.append(os.path.join(os.path.dirname(os.path.realpath(__file__)),
 from pylib import android_commands
 android_commands.GetAttachedDevices = lambda: ['0', '1']
 from pylib import constants
+from pylib.base import base_test_result
+from pylib.base import test_dispatcher
 from pylib.utils import watchdog_timer
 
-import base_test_result
-import test_dispatcher
 
 
 class TestException(Exception):
@@ -191,7 +193,7 @@ class TestShard(unittest.TestCase):
     android_commands.GetAttachedDevices = lambda: []
     try:
       with self.assertRaises(AssertionError):
-        results, exit_code = TestShard._RunShard(MockRunner)
+        _results, _exit_code = TestShard._RunShard(MockRunner)
     finally:
       android_commands.GetAttachedDevices = attached_devices