diff --git a/ros2trace_analysis/package.xml b/ros2trace_analysis/package.xml
index 2a3ebdf..47a2a53 100644
--- a/ros2trace_analysis/package.xml
+++ b/ros2trace_analysis/package.xml
@@ -13,6 +13,7 @@
 
   <test_depend>ament_copyright</test_depend>
   <test_depend>ament_flake8</test_depend>
+  <test_depend>ament_mypy</test_depend>
   <test_depend>ament_pep257</test_depend>
   <test_depend>ament_xmllint</test_depend>
   <test_depend>python3-pytest</test_depend>
diff --git a/ros2trace_analysis/test/test_mypy.py b/ros2trace_analysis/test/test_mypy.py
new file mode 100644
index 0000000..331a3b8
--- /dev/null
+++ b/ros2trace_analysis/test/test_mypy.py
@@ -0,0 +1,22 @@
+# Copyright 2019 Canonical Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from ament_mypy.main import main
+import pytest
+
+
+@pytest.mark.mypy
+@pytest.mark.linter
+def test_mypy():
+    assert main(argv=[]) == 0, 'Found errors'
diff --git a/tracetools_analysis/package.xml b/tracetools_analysis/package.xml
index 8bffec9..d9145b7 100644
--- a/tracetools_analysis/package.xml
+++ b/tracetools_analysis/package.xml
@@ -15,6 +15,7 @@
 
   <test_depend>ament_copyright</test_depend>
   <test_depend>ament_flake8</test_depend>
+  <test_depend>ament_mypy</test_depend>
   <test_depend>ament_pep257</test_depend>
   <test_depend>ament_xmllint</test_depend>
   <test_depend>python3-pytest</test_depend>
diff --git a/tracetools_analysis/test/test_mypy.py b/tracetools_analysis/test/test_mypy.py
new file mode 100644
index 0000000..331a3b8
--- /dev/null
+++ b/tracetools_analysis/test/test_mypy.py
@@ -0,0 +1,22 @@
+# Copyright 2019 Canonical Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from ament_mypy.main import main
+import pytest
+
+
+@pytest.mark.mypy
+@pytest.mark.linter
+def test_mypy():
+    assert main(argv=[]) == 0, 'Found errors'
diff --git a/tracetools_analysis/test/tracetools_analysis/test_autoprocessor.py b/tracetools_analysis/test/tracetools_analysis/test_autoprocessor.py
index 4bd4263..e94abe0 100644
--- a/tracetools_analysis/test/tracetools_analysis/test_autoprocessor.py
+++ b/tracetools_analysis/test/tracetools_analysis/test_autoprocessor.py
@@ -13,12 +13,13 @@
 # limitations under the License.
 
 from typing import Dict
-from typing import List
+from typing import Set
 import unittest
 
 from tracetools_analysis.processor import AutoProcessor
 from tracetools_analysis.processor import EventHandler
 from tracetools_analysis.processor import EventMetadata
+from tracetools_analysis.processor import HandlerMap
 
 
 class AbstractEventHandler(EventHandler):
@@ -32,18 +33,18 @@ class AbstractEventHandler(EventHandler):
 class SubSubEventHandler(AbstractEventHandler):
 
     def __init__(self) -> None:
-        handler_map = {
+        handler_map: HandlerMap = {
             'myeventname': self._handler_whatever,
             'myeventname69': self._handler_whatever,
         }
         super().__init__(handler_map=handler_map)
 
     @staticmethod
-    def required_events() -> List[str]:
-        return [
+    def required_events() -> Set[str]:
+        return {
             'myeventname',
             'myeventname69',
-        ]
+        }
 
     def _handler_whatever(
         self, event: Dict, metadata: EventMetadata
@@ -54,16 +55,16 @@ class SubSubEventHandler(AbstractEventHandler):
 class SubSubEventHandler2(AbstractEventHandler):
 
     def __init__(self) -> None:
-        handler_map = {
+        handler_map: HandlerMap = {
             'myeventname2': self._handler_whatever,
         }
         super().__init__(handler_map=handler_map)
 
     @staticmethod
-    def required_events() -> List[str]:
-        return [
+    def required_events() -> Set[str]:
+        return {
             'myeventname2',
-        ]
+        }
 
     def _handler_whatever(
         self, event: Dict, metadata: EventMetadata
@@ -74,16 +75,16 @@ class SubSubEventHandler2(AbstractEventHandler):
 class SubEventHandler(EventHandler):
 
     def __init__(self) -> None:
-        handler_map = {
+        handler_map: HandlerMap = {
             'myeventname3': self._handler_whatever,
         }
         super().__init__(handler_map=handler_map)
 
     @staticmethod
-    def required_events() -> List[str]:
-        return [
+    def required_events() -> Set[str]:
+        return {
             'myeventname3',
-        ]
+        }
 
     def _handler_whatever(
         self, event: Dict, metadata: EventMetadata
diff --git a/tracetools_analysis/test/tracetools_analysis/test_data_model_util.py b/tracetools_analysis/test/tracetools_analysis/test_data_model_util.py
index c7c8328..66f2cc3 100644
--- a/tracetools_analysis/test/tracetools_analysis/test_data_model_util.py
+++ b/tracetools_analysis/test/tracetools_analysis/test_data_model_util.py
@@ -23,6 +23,7 @@ from pandas.util.testing import assert_frame_equal
 from tracetools_analysis.data_model import DataModel
 from tracetools_analysis.processor import EventHandler
 from tracetools_analysis.processor import EventMetadata
+from tracetools_analysis.processor import HandlerMap
 from tracetools_analysis.utils import DataModelUtil
 
 
@@ -113,13 +114,13 @@ class TestDataModelUtil(unittest.TestCase):
         )
         assert_frame_equal(input_df, expected_df)
 
-    def test_creation(self) -> None:
-        def handler_whatever(
-            self, event: Dict, metadata: EventMetadata
-        ) -> None:
-            pass
+    def handler_whatever(
+        self, event: Dict, metadata: EventMetadata
+    ) -> None:
+        pass
 
-        handler_map = {'fake': handler_whatever}
+    def test_creation(self) -> None:
+        handler_map: HandlerMap = {'fake': self.handler_whatever}
         data_model = DataModel()
 
         # Should handle the event handler not having any data model
diff --git a/tracetools_analysis/test/tracetools_analysis/test_dependency_solver.py b/tracetools_analysis/test/tracetools_analysis/test_dependency_solver.py
index 91232aa..c225ac7 100644
--- a/tracetools_analysis/test/tracetools_analysis/test_dependency_solver.py
+++ b/tracetools_analysis/test/tracetools_analysis/test_dependency_solver.py
@@ -111,7 +111,7 @@ class TestDependencySolver(unittest.TestCase):
         # Pass parameter and check that the new instance has it
         solution = DependencySolver(depone_instance, myparam='myvalue').solve()
         self.assertEqual(len(solution), 2, 'solution length invalid')
-        self.assertEqual(solution[0].myparam, 'myvalue', 'parameter not passed on')
+        self.assertEqual(solution[0].myparam, 'myvalue', 'parameter not passed on')  # type: ignore
 
 
 if __name__ == '__main__':
diff --git a/tracetools_analysis/test/tracetools_analysis/test_process_command.py b/tracetools_analysis/test/tracetools_analysis/test_process_command.py
index 0eaaf8f..d076c9f 100644
--- a/tracetools_analysis/test/tracetools_analysis/test_process_command.py
+++ b/tracetools_analysis/test/tracetools_analysis/test_process_command.py
@@ -73,10 +73,10 @@ class TestProcessCommand(unittest.TestCase):
         # Should fail to find converted file under directory
         file_path, create_file = inspect_input_path(self.without_converted_file_dir, False)
         self.assertIsNone(file_path)
-        self.assertIsNone(create_file)
+        self.assertFalse(create_file)
         file_path, create_file = inspect_input_path(self.without_converted_file_dir, True)
         self.assertIsNone(file_path)
-        self.assertIsNone(create_file)
+        self.assertFalse(create_file)
 
         # Should accept any file path if it exists
         file_path, create_file = inspect_input_path(self.random_file_path, False)
diff --git a/tracetools_analysis/test/tracetools_analysis/test_processor.py b/tracetools_analysis/test/tracetools_analysis/test_processor.py
index af7f6c9..e523e15 100644
--- a/tracetools_analysis/test/tracetools_analysis/test_processor.py
+++ b/tracetools_analysis/test/tracetools_analysis/test_processor.py
@@ -13,18 +13,19 @@
 # limitations under the License.
 
 from typing import Dict
-from typing import List
+from typing import Set
 import unittest
 
 from tracetools_analysis.processor import EventHandler
 from tracetools_analysis.processor import EventMetadata
+from tracetools_analysis.processor import HandlerMap
 from tracetools_analysis.processor import Processor
 
 
 class StubHandler1(EventHandler):
 
     def __init__(self) -> None:
-        handler_map = {
+        handler_map: HandlerMap = {
             'myeventname': self._handler_whatever,
         }
         super().__init__(handler_map=handler_map)
@@ -39,7 +40,7 @@ class StubHandler1(EventHandler):
 class StubHandler2(EventHandler):
 
     def __init__(self) -> None:
-        handler_map = {
+        handler_map: HandlerMap = {
             'myeventname': self._handler_whatever,
         }
         super().__init__(handler_map=handler_map)
@@ -54,8 +55,8 @@ class StubHandler2(EventHandler):
 class WrongHandler(EventHandler):
 
     def __init__(self) -> None:
-        handler_map = {
-            'myeventname': self._handler_wrong,
+        handler_map: HandlerMap = {
+            'myeventname': self._handler_wrong,  # type: ignore # intentionally wrong
         }
         super().__init__(handler_map=handler_map)
 
@@ -68,17 +69,17 @@ class WrongHandler(EventHandler):
 class MissingEventHandler(EventHandler):
 
     def __init__(self) -> None:
-        handler_map = {
+        handler_map: HandlerMap = {
             'myeventname': self._handler_whatever,
         }
         super().__init__(handler_map=handler_map)
 
     @staticmethod
-    def required_events() -> List[str]:
-        return [
+    def required_events() -> Set[str]:
+        return {
             'no_handler_for_this',
             'myeventname',
-        ]
+        }
 
     def _handler_whatever(
         self, event: Dict, metadata: EventMetadata
@@ -89,16 +90,16 @@ class MissingEventHandler(EventHandler):
 class EventHandlerWithRequiredEvent(EventHandler):
 
     def __init__(self) -> None:
-        handler_map = {
+        handler_map: HandlerMap = {
             'myrequiredevent': self._handler_whatever,
         }
         super().__init__(handler_map=handler_map)
 
     @staticmethod
-    def required_events() -> List[str]:
-        return [
+    def required_events() -> Set[str]:
+        return {
             'myrequiredevent',
-        ]
+        }
 
     def _handler_whatever(
         self, event: Dict, metadata: EventMetadata
diff --git a/tracetools_analysis/test/tracetools_analysis/test_profile_handler.py b/tracetools_analysis/test/tracetools_analysis/test_profile_handler.py
index 05c3a8a..1fba862 100644
--- a/tracetools_analysis/test/tracetools_analysis/test_profile_handler.py
+++ b/tracetools_analysis/test/tracetools_analysis/test_profile_handler.py
@@ -316,8 +316,8 @@ class TestProfileHandler(unittest.TestCase):
         cls.processor.process(input_events)
 
     def test_profiling(self) -> None:
-        handler = self.__class__.handler
-        expected_df = self.__class__.expected
+        handler = self.__class__.handler  # type: ignore
+        expected_df = self.__class__.expected  # type: ignore
         result_df = handler.data.times
         assert_frame_equal(result_df, expected_df)
 
diff --git a/tracetools_analysis/tracetools_analysis/convert.py b/tracetools_analysis/tracetools_analysis/convert.py
index 5fe9660..336d2d1 100644
--- a/tracetools_analysis/tracetools_analysis/convert.py
+++ b/tracetools_analysis/tracetools_analysis/convert.py
@@ -19,7 +19,6 @@ import argparse
 import os
 import sys
 import time
-from typing import Optional
 
 from tracetools_analysis.conversion import ctf
 
@@ -50,7 +49,7 @@ def parse_args():
 def convert(
     trace_directory: str,
     output_file_name: str = DEFAULT_CONVERT_FILE_NAME,
-) -> Optional[int]:
+) -> int:
     """
     Convert trace directory to a file.
 
@@ -71,6 +70,7 @@ def convert(
     time_diff = time.time() - start_time
     print(f'converted {count} events in {time_diff_to_str(time_diff)}')
     print(f'output written to: {output_file_path}')
+    return 0
 
 
 def main():
diff --git a/tracetools_analysis/tracetools_analysis/data_model/__init__.py b/tracetools_analysis/tracetools_analysis/data_model/__init__.py
index 394c0db..c5cbe29 100644
--- a/tracetools_analysis/tracetools_analysis/data_model/__init__.py
+++ b/tracetools_analysis/tracetools_analysis/data_model/__init__.py
@@ -28,4 +28,4 @@ class DataModel():
 
     def print_data(self) -> None:
         """Print the data model."""
-        return None
+        raise NotImplementedError
diff --git a/tracetools_analysis/tracetools_analysis/data_model/memory_usage.py b/tracetools_analysis/tracetools_analysis/data_model/memory_usage.py
index 042888a..8eac7fc 100644
--- a/tracetools_analysis/tracetools_analysis/data_model/memory_usage.py
+++ b/tracetools_analysis/tracetools_analysis/data_model/memory_usage.py
@@ -52,5 +52,5 @@ class MemoryUsageDataModel(DataModel):
     def print_data(self) -> None:
         print('==================MEMORY USAGE DATA MODEL==================')
         tail = 20
-        print(f'Memory difference (tail={tail}):\n{self.times.tail(tail).to_string()}')
+        print(f'Memory difference (tail={tail}):\n{self.memory_diff.tail(tail).to_string()}')
         print('===========================================================')
diff --git a/tracetools_analysis/tracetools_analysis/data_model/profile.py b/tracetools_analysis/tracetools_analysis/data_model/profile.py
index c7ce318..0fcd1f8 100644
--- a/tracetools_analysis/tracetools_analysis/data_model/profile.py
+++ b/tracetools_analysis/tracetools_analysis/data_model/profile.py
@@ -14,6 +14,8 @@
 
 """Module for profile data model."""
 
+from typing import Optional
+
 import pandas as pd
 
 from . import DataModel
@@ -45,7 +47,7 @@ class ProfileDataModel(DataModel):
         tid: int,
         depth: int,
         function_name: str,
-        parent_name: str,
+        parent_name: Optional[str],
         start_timestamp: int,
         duration: int,
         actual_duration: int,
diff --git a/tracetools_analysis/tracetools_analysis/loading/__init__.py b/tracetools_analysis/tracetools_analysis/loading/__init__.py
index 1a74ee9..f6339be 100644
--- a/tracetools_analysis/tracetools_analysis/loading/__init__.py
+++ b/tracetools_analysis/tracetools_analysis/loading/__init__.py
@@ -19,6 +19,7 @@ import pickle
 import sys
 from typing import Dict
 from typing import List
+from typing import Optional
 from typing import Tuple
 
 from tracetools_read.trace import is_trace_directory
@@ -30,7 +31,7 @@ from ..convert import DEFAULT_CONVERT_FILE_NAME
 def inspect_input_path(
     input_path: str,
     force_conversion: bool = False,
-) -> Tuple[str, bool]:
+) -> Tuple[Optional[str], bool]:
     """
     Check input path for a converted file or a trace directory.
 
@@ -75,7 +76,7 @@ def inspect_input_path(
                 print(
                     f'cannot find either a trace directory or a converted file: {input_directory}',
                     file=sys.stderr)
-                return None, None
+                return None, False
     else:
         converted_file_path = input_path
         if force_conversion:
@@ -91,12 +92,13 @@ def inspect_input_path(
 def convert_if_needed(
     input_path: str,
     force_conversion: bool = False,
-) -> str:
+) -> Optional[str]:
     """
     Inspect input path and convert trace directory to file if necessary.
 
     :param input_path: the path to a converted file or trace directory
     :param force_conversion: whether to re-create converted file even if it is found
+    :return: the path to the converted file, or `None` if it failed
     """
     converted_file_path, create_converted_file = inspect_input_path(input_path, force_conversion)
 
@@ -130,6 +132,9 @@ def load_file(
     else:
         file_path = input_path
 
+    if file_path is None:
+        raise RuntimeError(f'could not use input path: {input_path}')
+
     events = []
     with open(os.path.expanduser(file_path), 'rb') as f:
         p = pickle.Unpickler(f)
diff --git a/tracetools_analysis/tracetools_analysis/process.py b/tracetools_analysis/tracetools_analysis/process.py
index d2cbe17..ca83445 100644
--- a/tracetools_analysis/tracetools_analysis/process.py
+++ b/tracetools_analysis/tracetools_analysis/process.py
@@ -19,7 +19,6 @@ import argparse
 import os
 import sys
 import time
-from typing import Optional
 
 from tracetools_analysis.loading import load_file
 from tracetools_analysis.processor import Processor
@@ -54,7 +53,7 @@ def process(
     input_path: str,
     force_conversion: bool = False,
     hide_results: bool = False,
-) -> Optional[int]:
+) -> int:
     """
     Process converted trace file.
 
@@ -77,6 +76,7 @@ def process(
     if not hide_results:
         processor.print_data()
     print(f'processed {len(events)} events in {time_diff_to_str(time_diff)}')
+    return 0
 
 
 def main():
diff --git a/tracetools_analysis/tracetools_analysis/processor/__init__.py b/tracetools_analysis/tracetools_analysis/processor/__init__.py
index a907262..9b5a585 100644
--- a/tracetools_analysis/tracetools_analysis/processor/__init__.py
+++ b/tracetools_analysis/tracetools_analysis/processor/__init__.py
@@ -16,9 +16,11 @@
 
 from collections import defaultdict
 import sys
+from types import ModuleType
 from typing import Callable
 from typing import Dict
 from typing import List
+from typing import Optional
 from typing import Set
 from typing import Type
 from typing import Union
@@ -80,8 +82,9 @@ class EventMetadata():
         return self._tid
 
 
-HandlerMap = Dict[str, Callable[[DictEvent, EventMetadata], None]]
-HandlerMultimap = Dict[str, List[Callable[[DictEvent, EventMetadata], None]]]
+HandlerMethod = Callable[[DictEvent, EventMetadata], None]
+HandlerMap = Dict[str, HandlerMethod]
+HandlerMultimap = Dict[str, List[HandlerMethod]]
 
 
 class Dependant():
@@ -92,6 +95,12 @@ class Dependant():
     Dependencies are type-related only.
     """
 
+    def __init__(
+        self,
+        **kwargs,
+    ) -> None:
+        pass
+
     @staticmethod
     def dependencies() -> List[Type['Dependant']]:
         """
@@ -116,7 +125,7 @@ class EventHandler(Dependant):
         self,
         *,
         handler_map: HandlerMap,
-        data_model: DataModel = None,
+        data_model: Optional[DataModel] = None,
         **kwargs,
     ) -> None:
         """
@@ -130,7 +139,7 @@ class EventHandler(Dependant):
         assert all(required_name in handler_map.keys() for required_name in self.required_events())
         self._handler_map = handler_map
         self._data_model = data_model
-        self._processor = None
+        self._processor: Optional[Processor] = None
 
     @property
     def handler_map(self) -> HandlerMap:
@@ -138,12 +147,12 @@ class EventHandler(Dependant):
         return self._handler_map
 
     @property
-    def data(self) -> Union[DataModel, None]:
+    def data(self) -> DataModel:
         """Get the data model."""
-        return self._data_model
+        return self._data_model  # type: ignore
 
     @property
-    def processor(self) -> 'Processor':
+    def processor(self) -> Optional['Processor']:
         return self._processor
 
     @staticmethod
@@ -154,7 +163,7 @@ class EventHandler(Dependant):
         Without these events, the EventHandler would be invalid/useless. Inheriting classes can
         decide not to declare that they require specific events.
         """
-        return {}
+        return set()
 
     def register_processor(
         self,
@@ -261,12 +270,11 @@ class DependencySolver():
                     solution,
                 )
             # If an instance of this type was given initially, use it instead
-            new_instance = None
-            if dep_type in initial_map:
-                new_instance = initial_map.get(dep_type)
+            dep_type_instance = initial_map.get(dep_type, None)
+            if dep_type_instance is not None:
+                solution.append(dep_type_instance)
             else:
-                new_instance = dep_type(**self._kwargs)
-            solution.append(new_instance)
+                solution.append(dep_type(**self._kwargs))
             visited.add(dep_type)
 
 
@@ -311,7 +319,7 @@ class Processor():
         :param handlers: the list of primary `EventHandler`s
         :param kwargs: the parameters to pass on to new instances
         """
-        return DependencySolver(*handlers, **kwargs).solve()
+        return DependencySolver(*handlers, **kwargs).solve()  # type: ignore
 
     @staticmethod
     def _get_handler_maps(
@@ -323,10 +331,10 @@ class Processor():
         :param handlers: the list of handlers
         :return: the merged multimap
         """
-        handler_multimap = defaultdict(list)
+        handler_multimap: HandlerMultimap = defaultdict(list)
         for handler in handlers:
-            for event_name, handler in handler.handler_map.items():
-                handler_multimap[event_name].append(handler)
+            for event_name, handler_method in handler.handler_map.items():
+                handler_multimap[event_name].append(handler_method)
         return handler_multimap
 
     def _register_with_handlers(
@@ -491,13 +499,13 @@ class AutoProcessor():
 
     @staticmethod
     def _get_applicable_event_handler_classes(
-        event_names: List[str],
-        handler_classes: List[Type[EventHandler]],
+        event_names: Set[str],
+        handler_classes: Set[Type[EventHandler]],
     ) -> Set[Type[EventHandler]]:
         """
-        Get applicable EventHandler subclasses for a list of event names.
+        Get applicable EventHandler subclasses for a set of event names.
 
-        :param event_names: the list of event names
+        :param event_names: the set of event names
         :return: a list of EventHandler subclasses for which requirements are met
         """
         return {
@@ -542,14 +550,19 @@ class AutoProcessor():
     @staticmethod
     def _import_event_handler_submodules(
         name: str = __name__,
-        recursive=True,
-    ):
-        """Force import of EventHandler submodules."""
+        recursive: bool = True,
+    ) -> Dict[str, ModuleType]:
+        """
+        Force import of EventHandler submodules.
+
+        :param name: the base module name
+        :param recursive: `True` if importing recursively, `False` otherwise
+        """
         import importlib
         import pkgutil
         package = importlib.import_module(name)
         results = {}
-        for loader, name, is_pkg in pkgutil.walk_packages(package.__path__):
+        for loader, name, is_pkg in pkgutil.walk_packages(package.__path__):  # type: ignore #1422
             full_name = package.__name__ + '.' + name
             results[full_name] = importlib.import_module(full_name)
             if recursive and is_pkg:
@@ -570,10 +583,10 @@ class ProcessingProgressDisplay():
         :param processing_elements: the list of elements doing processing
         """
         self.__info_string = '[' + ', '.join(processing_elements) + ']'
-        self.__total_work = None
-        self.__progress_count = None
-        self.__rolling_count = None
-        self.__work_display_period = None
+        self.__total_work: int = 0
+        self.__progress_count: int = 0
+        self.__rolling_count: int = 0
+        self.__work_display_period: int = 0
 
     def set_work_total(
         self,
diff --git a/tracetools_analysis/tracetools_analysis/processor/cpu_time.py b/tracetools_analysis/tracetools_analysis/processor/cpu_time.py
index 1190448..362d56f 100644
--- a/tracetools_analysis/tracetools_analysis/processor/cpu_time.py
+++ b/tracetools_analysis/tracetools_analysis/processor/cpu_time.py
@@ -21,6 +21,7 @@ from tracetools_read import get_field
 
 from . import EventHandler
 from . import EventMetadata
+from . import HandlerMap
 from ..data_model.cpu_time import CpuTimeDataModel
 
 
@@ -37,7 +38,7 @@ class CpuTimeHandler(EventHandler):
     ) -> None:
         """Create a CpuTimeHandler."""
         # Link event to handling method
-        handler_map = {
+        handler_map: HandlerMap = {
             'sched_switch':
                 self._handle_sched_switch,
         }
@@ -57,6 +58,10 @@ class CpuTimeHandler(EventHandler):
             'sched_switch',
         }
 
+    @property
+    def data(self) -> CpuTimeDataModel:
+        return super().data  # type: ignore
+
     def _handle_sched_switch(
         self, event: Dict, metadata: EventMetadata
     ) -> None:
diff --git a/tracetools_analysis/tracetools_analysis/processor/memory_usage.py b/tracetools_analysis/tracetools_analysis/processor/memory_usage.py
index f26e91a..e0bf4bf 100644
--- a/tracetools_analysis/tracetools_analysis/processor/memory_usage.py
+++ b/tracetools_analysis/tracetools_analysis/processor/memory_usage.py
@@ -21,6 +21,7 @@ from tracetools_read import get_field
 
 from . import EventHandler
 from . import EventMetadata
+from . import HandlerMap
 from ..data_model.memory_usage import MemoryUsageDataModel
 
 
@@ -38,6 +39,10 @@ class MemoryUsageHandler(EventHandler):
             **kwargs,
         )
 
+    @property
+    def data(self) -> MemoryUsageDataModel:
+        return super().data  # type: ignore
+
     def _update(
         self,
         timestamp: int,
@@ -72,7 +77,7 @@ class UserspaceMemoryUsageHandler(MemoryUsageHandler):
         **kwargs,
     ) -> None:
         # Link event to handling method
-        handler_map = {
+        handler_map: HandlerMap = {
             'lttng_ust_libc:malloc':
                 self._handle_malloc,
             'lttng_ust_libc:calloc':
@@ -196,7 +201,7 @@ class KernelMemoryUsageHandler(MemoryUsageHandler):
         **kwargs,
     ) -> None:
         # Link event to handling method
-        handler_map = {
+        handler_map: HandlerMap = {
             'kmem_mm_page_alloc':
                 self._handle_malloc,
             'kmem_mm_page_free':
diff --git a/tracetools_analysis/tracetools_analysis/processor/profile.py b/tracetools_analysis/tracetools_analysis/processor/profile.py
index 16e2246..7e6a5c7 100644
--- a/tracetools_analysis/tracetools_analysis/processor/profile.py
+++ b/tracetools_analysis/tracetools_analysis/processor/profile.py
@@ -24,7 +24,7 @@ from tracetools_read import get_field
 
 from . import EventHandler
 from . import EventMetadata
-
+from . import HandlerMap
 from ..data_model.profile import ProfileDataModel
 
 
@@ -56,7 +56,7 @@ class ProfileHandler(EventHandler):
 
         :param address_to_func: the mapping from function address (`int` or hex `str`) to name
         """
-        handler_map = {
+        handler_map: HandlerMap = {
             'lttng_ust_cyg_profile_fast:func_entry':
                 self._handle_function_entry,
             'lttng_ust_cyg_profile_fast:func_exit':
@@ -95,6 +95,10 @@ class ProfileHandler(EventHandler):
             'sched_switch',
         }
 
+    @property
+    def data(self) -> ProfileDataModel:
+        return super().data  # type: ignore
+
     @staticmethod
     def addr_to_int(addr: Union[int, str]) -> int:
         """Transform an address into an `int` if it's a hex `str`."""
@@ -106,20 +110,22 @@ class ProfileHandler(EventHandler):
         timestamp = metadata.timestamp
         # If function(s) currently running stop(s) executing
         prev_tid = get_field(event, 'prev_tid')
-        if prev_tid in self._current_funcs:
+        prev_info_list = self._current_funcs.get(prev_tid, None)
+        if prev_info_list is not None:
             # Increment durations using last start timestamp
-            for info in self._current_funcs.get(prev_tid):
+            for info in prev_info_list:
                 last_start = info[2]
                 total_duration = info[3]
                 total_duration += timestamp - last_start
-                info[2] = None
+                info[2] = -1
                 info[3] = total_duration
         # If stopped function(s) start(s) executing again
         next_tid = get_field(event, 'next_tid')
-        if next_tid in self._current_funcs:
+        next_info_list = self._current_funcs.get(next_tid, None)
+        if next_info_list is not None:
             # Set last start timestamp to now
-            for info in self._current_funcs.get(next_tid):
-                assert info[2] is None
+            for info in next_info_list:
+                assert info[2] == -1
                 info[2] = timestamp
 
     def _handle_function_entry(
@@ -153,9 +159,9 @@ class ProfileHandler(EventHandler):
         self.data.add_duration(
             tid,
             function_depth,
-            function_name,
-            parent_name,
-            start_timestamp,
+            function_name,  # type: ignore
+            parent_name,  # type: ignore
+            start_timestamp,  # type: ignore
             duration,
             actual_duration,
         )
diff --git a/tracetools_analysis/tracetools_analysis/processor/ros2.py b/tracetools_analysis/tracetools_analysis/processor/ros2.py
index 465ef7d..e46d5b4 100644
--- a/tracetools_analysis/tracetools_analysis/processor/ros2.py
+++ b/tracetools_analysis/tracetools_analysis/processor/ros2.py
@@ -16,11 +16,13 @@
 
 from typing import Dict
 from typing import Set
+from typing import Tuple
 
 from tracetools_read import get_field
 
 from . import EventHandler
 from . import EventMetadata
+from . import HandlerMap
 from ..data_model.ros2 import Ros2DataModel
 
 
@@ -37,7 +39,7 @@ class Ros2Handler(EventHandler):
     ) -> None:
         """Create a Ros2Handler."""
         # Link a ROS trace event to its corresponding handling method
-        handler_map = {
+        handler_map: HandlerMap = {
             'ros2:rcl_init':
                 self._handle_rcl_init,
             'ros2:rcl_node_init':
@@ -74,7 +76,7 @@ class Ros2Handler(EventHandler):
         )
 
         # Temporary buffers
-        self._callback_instances = {}
+        self._callback_instances: Dict[int, Tuple[Dict, EventMetadata]] = {}
 
     @staticmethod
     def required_events() -> Set[str]:
@@ -82,6 +84,10 @@ class Ros2Handler(EventHandler):
             'ros2:rcl_init',
         }
 
+    @property
+    def data(self) -> Ros2DataModel:
+        return super().data  # type: ignore
+
     def _handle_rcl_init(
         self, event: Dict, metadata: EventMetadata,
     ) -> None:
@@ -207,8 +213,9 @@ class Ros2Handler(EventHandler):
     ) -> None:
         # Fetch from dict
         callback_object = get_field(event, 'callback')
-        (event_start, metadata_start) = self._callback_instances.get(callback_object)
-        if event_start is not None and metadata_start is not None:
+        callback_instance_data = self._callback_instances.get(callback_object)
+        if callback_instance_data is not None:
+            (event_start, metadata_start) = callback_instance_data
             del self._callback_instances[callback_object]
             duration = metadata.timestamp - metadata_start.timestamp
             is_intra_process = get_field(event_start, 'is_intra_process', raise_if_not_found=False)
diff --git a/tracetools_analysis/tracetools_analysis/utils/__init__.py b/tracetools_analysis/tracetools_analysis/utils/__init__.py
index 27333ce..3074c3a 100644
--- a/tracetools_analysis/tracetools_analysis/utils/__init__.py
+++ b/tracetools_analysis/tracetools_analysis/utils/__init__.py
@@ -16,6 +16,7 @@
 
 from datetime import datetime as dt
 from typing import List
+from typing import Optional
 from typing import Union
 
 from pandas import DataFrame
@@ -43,7 +44,7 @@ class DataModelUtil():
         self.__data = data_object.data if isinstance(data_object, EventHandler) else data_object
 
     @property
-    def data(self) -> Union[DataModel, None]:
+    def data(self) -> Optional[DataModel]:
         return self.__data
 
     @staticmethod
diff --git a/tracetools_analysis/tracetools_analysis/utils/cpu_time.py b/tracetools_analysis/tracetools_analysis/utils/cpu_time.py
index dee8eba..e7a92df 100644
--- a/tracetools_analysis/tracetools_analysis/utils/cpu_time.py
+++ b/tracetools_analysis/tracetools_analysis/utils/cpu_time.py
@@ -37,6 +37,10 @@ class CpuTimeDataModelUtil(DataModelUtil):
         """
         super().__init__(data_object)
 
+    @property
+    def data(self) -> CpuTimeDataModel:
+        return super().data  # type: ignore
+
     def get_time_per_thread(self) -> DataFrame:
         """Get a DataFrame of total duration for each thread."""
         return self.data.times.loc[:, ['tid', 'duration']].groupby(by='tid').sum()
diff --git a/tracetools_analysis/tracetools_analysis/utils/memory_usage.py b/tracetools_analysis/tracetools_analysis/utils/memory_usage.py
index 3835f46..4b81e92 100644
--- a/tracetools_analysis/tracetools_analysis/utils/memory_usage.py
+++ b/tracetools_analysis/tracetools_analysis/utils/memory_usage.py
@@ -16,6 +16,8 @@
 
 from collections import defaultdict
 from typing import Dict
+from typing import List
+from typing import Optional
 from typing import Union
 
 from pandas import DataFrame
@@ -66,12 +68,13 @@ class MemoryUsageDataModelUtil(DataModelUtil):
         """
         suffixes = ['B', 'KB', 'MB', 'GB', 'TB']
         suffixIndex = 0
-        while size > 1024 and suffixIndex < 4:
+        mem_size = float(size)
+        while mem_size > 1024.0 and suffixIndex < 4:
             # Increment the index of the suffix
             suffixIndex += 1
             # Apply the division
-            size = size / 1024.0
-        return f'{size:.{precision}f} {suffixes[suffixIndex]}'
+            mem_size = mem_size / 1024.0
+        return f'{mem_size:.{precision}f} {suffixes[suffixIndex]}'
 
     def get_max_memory_usage_per_tid(self) -> DataFrame:
         """
@@ -79,50 +82,61 @@ class MemoryUsageDataModelUtil(DataModelUtil):
 
         :return dataframe with maximum memory usage (userspace & kernel) per tid
         """
-        if self.data_ust is not None:
-            ust_memory_usage_dfs = self.get_absolute_userspace_memory_usage_by_tid()
+        tids_ust = None
+        tids_kernel = None
+        ust_memory_usage_dfs = self.get_absolute_userspace_memory_usage_by_tid()
+        if ust_memory_usage_dfs is not None:
             tids_ust = set(ust_memory_usage_dfs.keys())
-        if self.data_kernel is not None:
-            kernel_memory_usage_dfs = self.get_absolute_kernel_memory_usage_by_tid()
+        kernel_memory_usage_dfs = self.get_absolute_kernel_memory_usage_by_tid()
+        if kernel_memory_usage_dfs is not None:
             tids_kernel = set(kernel_memory_usage_dfs.keys())
         # Use only the userspace tid values if available, otherwise use the kernel tid values
-        tids = tids_ust if self.data_ust is not None else tids_kernel
+        tids = tids_ust or tids_kernel
+        # Should not happen, since it is checked in __init__
+        if tids is None:
+            raise RuntimeError('no data')
         data = [
             [
                 tid,
                 self.format_size(ust_memory_usage_dfs[tid]['memory_usage'].max(), precision=1)
-                if self.data_ust is not None
+                if ust_memory_usage_dfs is not None
+                and ust_memory_usage_dfs.get(tid) is not None
                 else None,
                 self.format_size(kernel_memory_usage_dfs[tid]['memory_usage'].max(), precision=1)
-                if self.data_kernel is not None and ust_memory_usage_dfs.get(tid) is not None
+                if kernel_memory_usage_dfs is not None
+                and kernel_memory_usage_dfs.get(tid) is not None
                 else None,
             ]
             for tid in tids
         ]
         return DataFrame(data, columns=['tid', 'max_memory_usage_ust', 'max_memory_usage_kernel'])
 
-    def get_absolute_userspace_memory_usage_by_tid(self) -> Dict[int, DataFrame]:
+    def get_absolute_userspace_memory_usage_by_tid(self) -> Optional[Dict[int, DataFrame]]:
         """
         Get absolute userspace memory usage over time per tid.
 
         :return (tid -> DataFrame of absolute memory usage over time)
         """
+        if self.data_ust is None:
+            return None
         return self._get_absolute_memory_usage_by_tid(self.data_ust)
 
-    def get_absolute_kernel_memory_usage_by_tid(self) -> Dict[int, DataFrame]:
+    def get_absolute_kernel_memory_usage_by_tid(self) -> Optional[Dict[int, DataFrame]]:
         """
         Get absolute kernel memory usage over time per tid.
 
         :return (tid -> DataFrame of absolute memory usage over time)
         """
+        if self.data_kernel is None:
+            return None
         return self._get_absolute_memory_usage_by_tid(self.data_kernel)
 
     def _get_absolute_memory_usage_by_tid(
         self,
         data_model: MemoryUsageDataModel,
     ) -> Dict[int, DataFrame]:
-        previous = defaultdict(int)
-        data = defaultdict(list)
+        previous: Dict[int, int] = defaultdict(int)
+        data: Dict[int, List[Dict[str, int]]] = defaultdict(list)
         for index, row in data_model.memory_diff.iterrows():
             timestamp = row['timestamp']
             tid = int(row['tid'])
diff --git a/tracetools_analysis/tracetools_analysis/utils/profile.py b/tracetools_analysis/tracetools_analysis/utils/profile.py
index e25ae79..1d8a3bb 100644
--- a/tracetools_analysis/tracetools_analysis/utils/profile.py
+++ b/tracetools_analysis/tracetools_analysis/utils/profile.py
@@ -41,6 +41,10 @@ class ProfileDataModelUtil(DataModelUtil):
         """
         super().__init__(data_object)
 
+    @property
+    def data(self) -> ProfileDataModel:
+        return super().data  # type: ignore
+
     def with_tid(
         self,
         tid: int,
@@ -54,12 +58,12 @@ class ProfileDataModelUtil(DataModelUtil):
     def get_call_tree(
         self,
         tid: int,
-    ) -> Dict[str, List[str]]:
+    ) -> Dict[str, Set[str]]:
         depth_names = self.with_tid(tid)[
             ['depth', 'function_name', 'parent_name']
         ].drop_duplicates()
         # print(depth_names.to_string())
-        tree = defaultdict(set)
+        tree: Dict[str, Set[str]] = defaultdict(set)
         for _, row in depth_names.iterrows():
             depth = row['depth']
             name = row['function_name']
diff --git a/tracetools_analysis/tracetools_analysis/utils/ros2.py b/tracetools_analysis/tracetools_analysis/utils/ros2.py
index de39ae6..7b186ad 100644
--- a/tracetools_analysis/tracetools_analysis/utils/ros2.py
+++ b/tracetools_analysis/tracetools_analysis/utils/ros2.py
@@ -18,6 +18,7 @@
 from typing import Any
 from typing import List
 from typing import Mapping
+from typing import Optional
 from typing import Union
 
 from pandas import DataFrame
@@ -41,6 +42,10 @@ class Ros2DataModelUtil(DataModelUtil):
         """
         super().__init__(data_object)
 
+    @property
+    def data(self) -> Ros2DataModel:
+        return super().data  # type: ignore
+
     def _prettify(
         self,
         original: str,
@@ -140,7 +145,7 @@ class Ros2DataModelUtil(DataModelUtil):
     def get_node_tid_from_name(
         self,
         node_name: str,
-    ) -> Union[int, None]:
+    ) -> Optional[int]:
         """
         Get the tid corresponding to a node.
 
@@ -157,7 +162,7 @@ class Ros2DataModelUtil(DataModelUtil):
     def get_node_names_from_tid(
         self,
         tid: str,
-    ) -> Union[List[str], None]:
+    ) -> Optional[List[str]]:
         """
         Get the list of node names corresponding to a tid.
 
@@ -171,7 +176,7 @@ class Ros2DataModelUtil(DataModelUtil):
     def get_callback_owner_info(
         self,
         callback_obj: int,
-    ) -> Union[str, None]:
+    ) -> Optional[str]:
         """
         Get information about the owner of a callback.
 
@@ -207,9 +212,9 @@ class Ros2DataModelUtil(DataModelUtil):
             type_name = 'Client'
             info = self.get_client_handle_info(reference)
 
-        if info is not None:
-            info = f'{type_name} -- {self.format_info_dict(info)}'
-        return info
+        if info is None:
+            return None
+        return f'{type_name} -- {self.format_info_dict(info)}'
 
     def get_timer_handle_info(
         self,
@@ -245,6 +250,8 @@ class Ros2DataModelUtil(DataModelUtil):
 
         node_handle = self.data.publishers.loc[publisher_handle, 'node_handle']
         node_handle_info = self.get_node_handle_info(node_handle)
+        if node_handle_info is None:
+            return None
         topic_name = self.data.publishers.loc[publisher_handle, 'topic_name']
         publisher_info = {'topic': topic_name}
         return {**node_handle_info, **publisher_info}
@@ -252,7 +259,7 @@ class Ros2DataModelUtil(DataModelUtil):
     def get_subscription_reference_info(
         self,
         subscription_reference: int,
-    ) -> Union[Mapping[str, Any], None]:
+    ) -> Optional[Mapping[str, Any]]:
         """
         Get information about a subscription handle.
 
@@ -297,6 +304,8 @@ class Ros2DataModelUtil(DataModelUtil):
 
         node_handle = subscriptions_info.loc[subscription_reference, 'node_handle']
         node_handle_info = self.get_node_handle_info(node_handle)
+        if node_handle_info is None:
+            return None
         topic_name = subscriptions_info.loc[subscription_reference, 'topic_name']
         subscription_info = {'topic': topic_name}
         return {**node_handle_info, **subscription_info}
@@ -304,7 +313,7 @@ class Ros2DataModelUtil(DataModelUtil):
     def get_service_handle_info(
         self,
         service_handle: int,
-    ) -> Union[Mapping[str, Any], None]:
+    ) -> Optional[Mapping[str, Any]]:
         """
         Get information about a service handle.
 
@@ -316,6 +325,8 @@ class Ros2DataModelUtil(DataModelUtil):
 
         node_handle = self.data.services.loc[service_handle, 'node_handle']
         node_handle_info = self.get_node_handle_info(node_handle)
+        if node_handle_info is None:
+            return None
         service_name = self.data.services.loc[service_handle, 'service_name']
         service_info = {'service': service_name}
         return {**node_handle_info, **service_info}
@@ -323,7 +334,7 @@ class Ros2DataModelUtil(DataModelUtil):
     def get_client_handle_info(
         self,
         client_handle: int,
-    ) -> Union[Mapping[str, Any], None]:
+    ) -> Optional[Mapping[str, Any]]:
         """
         Get information about a client handle.
 
@@ -335,6 +346,8 @@ class Ros2DataModelUtil(DataModelUtil):
 
         node_handle = self.data.clients.loc[client_handle, 'node_handle']
         node_handle_info = self.get_node_handle_info(node_handle)
+        if node_handle_info is None:
+            return None
         service_name = self.data.clients.loc[client_handle, 'service_name']
         service_info = {'service': service_name}
         return {**node_handle_info, **service_info}
@@ -342,7 +355,7 @@ class Ros2DataModelUtil(DataModelUtil):
     def get_node_handle_info(
         self,
         node_handle: int,
-    ) -> Union[Mapping[str, Any], None]:
+    ) -> Optional[Mapping[str, Any]]:
         """
         Get information about a node handle.