4 files changed, 14 insertions, 20 deletions

diff --git a/glucometerutils/support/contourusb.py b/glucometerutils/support/contourusb.py
index 3b0dc80..9afb79d 100644
--- a/glucometerutils/support/contourusb.py
+++ b/glucometerutils/support/contourusb.py
@@ -180,14 +180,14 @@ class ContourHidDevice(hiddevice.HidDevice):
 
         if recno != self.currecno:
             raise FrameError(
-                "Bad recno, got %r expected %r" % (recno, self.currecno), frame
+                f"Bad recno, got {recno!r} expected {self.currecno!r}", frame
             )
 
-        checksum = self.checksum(match.group("check"))
-        if checksum != match.group("checksum"):
+        calculated_checksum = self.checksum(match.group("check"))
+        received_checksum = match.group("checksum")
+        if calculated_checksum != received_checksum:
             raise FrameError(
-                "Checksum error: got %s expected %s"
-                % (match.group("checksum"), checksum),
+                f"Checksum error: received {received_checksum} expected {calculated_checksum}",
                 frame,
             )
 
diff --git a/glucometerutils/support/freestyle.py b/glucometerutils/support/freestyle.py
index 341e978..86c53d0 100644
--- a/glucometerutils/support/freestyle.py
+++ b/glucometerutils/support/freestyle.py
@@ -152,8 +152,7 @@ class FreeStyleHidDevice(hiddevice.HidDevice, driver_base.GlucometerDriver, ABC)
         response = self._read_response()
         if not _is_init_reply(response):
             raise exceptions.ConnectionFailed(
-                "Connection error: unexpected message %02x:%s"
-                % (response[0], response[1].hex())
+                f"Connection error: unexpected message %{response[0]:02x}:{response[1].hex()}"
             )
 
     def disconnect(self):
@@ -235,8 +234,7 @@ class FreeStyleHidDevice(hiddevice.HidDevice, driver_base.GlucometerDriver, ABC)
 
             if message_type != self.TEXT_REPLY_CMD:
                 raise exceptions.InvalidResponse(
-                    "Message type %02x does not match expectations: %r"
-                    % (message_type, content)
+                    f"Message type {message_type:02x}: content does not match expectations: {content!r}"
                 )
 
             full_content += content
@@ -317,10 +315,8 @@ class FreeStyleHidDevice(hiddevice.HidDevice, driver_base.GlucometerDriver, ABC)
         # The format used by the FreeStyle devices is not composable based on
         # standard strftime() (namely it includes no leading zeros), so we need
         # to build it manually.
-        date_cmd = "$date,{month},{day},{year}".format(
-            month=date.month, day=date.day, year=(date.year - 2000)
-        )
-        time_cmd = "$time,{hour},{minute}".format(hour=date.hour, minute=date.minute)
+        date_cmd = f"$date,{date.month},{date.day},{date.year - 2000}"
+        time_cmd = f"$time,{date.hour},{date.minute}"
 
         self._send_text_command(bytes(date_cmd, "ascii"))
         self._send_text_command(bytes(time_cmd, "ascii"))
diff --git a/glucometerutils/support/hiddevice.py b/glucometerutils/support/hiddevice.py
index ad8f3a6..43461e7 100644
--- a/glucometerutils/support/hiddevice.py
+++ b/glucometerutils/support/hiddevice.py
@@ -52,9 +52,7 @@ class HidDevice:
         # If the user passed a device path that does not exist, raise an
         # error. This is to avoid writing to a file instead of to a device node.
         if device and not os.path.exists(device):
-            raise exceptions.ConnectionFailed(
-                message="Path %s does not exist." % device
-            )
+            raise exceptions.ConnectionFailed(message=f"Path {device} does not exist.")
 
         # If the user passed a device, try opening it.
         if device:
@@ -73,7 +71,7 @@ class HidDevice:
                 )
             except OSError as e:
                 raise exceptions.ConnectionFailed(
-                    message="Unable to connect to meter: %s." % e
+                    message=f"Unable to connect to meter: {e}."
                 )
 
     def _write(self, report):
diff --git a/glucometerutils/support/lifescan.py b/glucometerutils/support/lifescan.py
index 9340e49..1c329c6 100644
--- a/glucometerutils/support/lifescan.py
+++ b/glucometerutils/support/lifescan.py
@@ -11,7 +11,7 @@ class MissingChecksum(exceptions.InvalidResponse):
 
     def __init__(self, response):
         super(MissingChecksum, self).__init__(
-            "Response is missing checksum: %s" % response
+            f"Response is missing checksum: {response}"
         )
 
 
@@ -20,13 +20,13 @@ class InvalidSerialNumber(exceptions.Error):
 
     def __init__(self, serial_number):
         super(InvalidSerialNumber, self).__init__(
-            "Serial number %s is invalid." % serial_number
+            f"Serial number {serial_number} is invalid."
         )
 
 
 class MalformedCommand(exceptions.InvalidResponse):
     def __init__(self, message):
-        super(MalformedCommand, self).__init__("Malformed command: %s" % message)
+        super(MalformedCommand, self).__init__(f"Malformed command: {message}")
 
 
 def crc_ccitt(data):