1 files changed, 19 insertions, 16 deletions
diff --git a/glucometerutils/exceptions.py b/glucometerutils/exceptions.py
index 1f72308..d56dbe6 100644
--- a/glucometerutils/exceptions.py
+++ b/glucometerutils/exceptions.py
@@ -3,6 +3,8 @@
 # SPDX-License-Identifier: MIT
 """Common exceptions for glucometerutils."""
 
+from typing import Any, Optional
+
 
 class Error(Exception):
     """Base class for the errors."""
@@ -15,42 +17,43 @@ class CommandLineError(Error):
 class ConnectionFailed(Error):
     """It was not possible to connect to the meter."""
 
-    def __init__(self, message="Unable to connect to the meter."):
-        super(ConnectionFailed, self).__init__(message)
+    def __init__(self, message: str = "Unable to connect to the meter.") -> None:
+        super().__init__(message)
 
 
 class CommandError(Error):
     """It was not possible to send a command to the device."""
 
-    def __init__(self, message="Unable to send command to device."):
-        super(CommandError, self).__init__(message)
+    def __init__(self, message: str = "Unable to send command to device.") -> None:
+        super().__init__(message)
 
 
 class InvalidResponse(Error):
     """The response received from the meter was not understood"""
 
-    def __init__(self, response):
-        super(InvalidResponse, self).__init__(f"Invalid response received:\n{response}")
+    def __init__(self, response: str) -> None:
+        super().__init__(f"Invalid response received:\n{response}")
 
 
 class InvalidChecksum(InvalidResponse):
-    def __init__(self, wire, calculated):
-        super(InvalidChecksum, self).__init__(
-            f"Response checksum not matching: {wire:08x} (wire) != {calculated:08x} (calculated)"
-        )
+    def __init__(self, wire: int, calculated: Optional[int]) -> None:
+        if calculated is not None:
+            message = f"Response checksum not matching: {wire:08x} (wire) != {calculated:08x} (calculated)"
+        else:
+            message = f"Unable to calculate checksum. Expected {wire:08x}."
+
+        super().__init__(message)
 
 
 class InvalidGlucoseUnit(Error):
     """Unable to parse the given glucose unit"""
 
-    def __init__(self, unit):
-        super(InvalidGlucoseUnit, self).__init__(
-            f"Invalid glucose unit received:\n{unit}"
-        )
+    def __init__(self, unit: Any) -> None:
+        super().__init__(f"Invalid glucose unit received:\n{unit}")
 
 
 class InvalidDateTime(Error):
     """The device has an invalid date/time setting."""
 
-    def __init__(self):
-        super(InvalidDateTime, self).__init__("Invalid date and time for device")
+    def __init__(self) -> None:
+        super().__init__("Invalid date and time for device")