diff --git a/.flake8 b/.flake8
index acb20bc..6527ed8 100644
--- a/.flake8
+++ b/.flake8
@@ -2,4 +2,4 @@
 exclude = .git,.lock
 max-complexity = 10
 max-line-length = 90
-ignore=E501
+ignore=E501,W503
diff --git a/src/prometheus_fastapi_instrumentator/instrumentation.py b/src/prometheus_fastapi_instrumentator/instrumentation.py
index c88eae3..286f07f 100644
--- a/src/prometheus_fastapi_instrumentator/instrumentation.py
+++ b/src/prometheus_fastapi_instrumentator/instrumentation.py
@@ -2,7 +2,7 @@
 import os
 import re
 from enum import Enum
-from typing import Callable, List, Optional, Pattern, Union
+from typing import Callable, List, Optional, Union
 
 from fastapi import FastAPI
 from starlette.requests import Request
@@ -23,7 +23,7 @@ def __init__(
         should_round_latency_decimals: bool = False,
         should_respect_env_var: bool = False,
         should_instrument_requests_inprogress: bool = False,
-        excluded_handlers: List[str] = [],
+        excluded_handlers: List[str] = None,
         round_latency_decimals: int = 4,
         env_var_name: str = "ENABLE_METRICS",
         inprogress_name: str = "http_requests_inprogress",
@@ -90,11 +90,10 @@ def __init__(
         self.inprogress_name = inprogress_name
         self.inprogress_labels = inprogress_labels
 
-        self.excluded_handlers: List[Pattern[str]]
-        if excluded_handlers:
-            self.excluded_handlers = [re.compile(path) for path in excluded_handlers]
-        else:
-            self.excluded_handlers = []
+        if excluded_handlers is None:
+            excluded_handlers = []
+
+        self.excluded_handlers = [re.compile(path) for path in excluded_handlers]
 
         self.instrumentations: List[Callable[[metrics.Info], None]] = []
 
@@ -207,11 +206,11 @@ def metrics(request: Request):
                 resp = Response(content=gzip.compress(generate_latest(registry)))
                 resp.headers["Content-Type"] = CONTENT_TYPE_LATEST
                 resp.headers["Content-Encoding"] = "gzip"
-                return resp
             else:
                 resp = Response(content=generate_latest(registry))
                 resp.headers["Content-Type"] = CONTENT_TYPE_LATEST
-                return resp
+
+            return resp
 
         return self
 
diff --git a/src/prometheus_fastapi_instrumentator/metrics.py b/src/prometheus_fastapi_instrumentator/metrics.py
index b468fed..c965b9d 100644
--- a/src/prometheus_fastapi_instrumentator/metrics.py
+++ b/src/prometheus_fastapi_instrumentator/metrics.py
@@ -162,9 +162,10 @@ def latency(
 
     def instrumentation(info: Info) -> None:
         if label_names:
-            label_values = []
-            for attribute_name in info_attribute_names:
-                label_values.append(getattr(info, attribute_name))
+            label_values = [
+                getattr(info, attribute_name) for attribute_name in info_attribute_names
+            ]
+
             METRIC.labels(*label_values).observe(info.modified_duration)
         else:
             METRIC.observe(info.modified_duration)
@@ -228,9 +229,10 @@ def request_size(
     def instrumentation(info: Info) -> None:
         content_length = info.request.headers.get("Content-Length", 0)
         if label_names:
-            label_values = []
-            for attribute_name in info_attribute_names:
-                label_values.append(getattr(info, attribute_name))
+            label_values = [
+                getattr(info, attribute_name) for attribute_name in info_attribute_names
+            ]
+
             METRIC.labels(*label_values).observe(int(content_length))
         else:
             METRIC.observe(int(content_length))
@@ -304,9 +306,10 @@ def instrumentation(info: Info) -> None:
             content_length = 0
 
         if label_names:
-            label_values = []
-            for attribute_name in info_attribute_names:
-                label_values.append(getattr(info, attribute_name))
+            label_values = [
+                getattr(info, attribute_name) for attribute_name in info_attribute_names
+            ]
+
             METRIC.labels(*label_values).observe(int(content_length))
         else:
             METRIC.observe(int(content_length))
@@ -384,9 +387,10 @@ def instrumentation(info: Info) -> None:
         content_length = int(request_cl) + int(response_cl)
 
         if label_names:
-            label_values = []
-            for attribute_name in info_attribute_names:
-                label_values.append(getattr(info, attribute_name))
+            label_values = [
+                getattr(info, attribute_name) for attribute_name in info_attribute_names
+            ]
+
             METRIC.labels(*label_values).observe(int(content_length))
         else:
             METRIC.observe(int(content_length))
@@ -453,9 +457,10 @@ def requests(
 
     def instrumentation(info: Info) -> None:
         if label_names:
-            label_values = []
-            for attribute_name in info_attribute_names:
-                label_values.append(getattr(info, attribute_name))
+            label_values = [
+                getattr(info, attribute_name) for attribute_name in info_attribute_names
+            ]
+
             METRIC.labels(*label_values).inc()
         else:
             METRIC.inc()
diff --git a/src/prometheus_fastapi_instrumentator/middleware.py b/src/prometheus_fastapi_instrumentator/middleware.py
index 36b90c5..1fa936d 100644
--- a/src/prometheus_fastapi_instrumentator/middleware.py
+++ b/src/prometheus_fastapi_instrumentator/middleware.py
@@ -160,7 +160,7 @@ def _is_handler_excluded(self, handler: str, is_templated: bool) -> bool:
             bool: `True` if excluded, `False` if not.
         """
 
-        if is_templated is False and self.should_ignore_untemplated:
+        if not is_templated and self.should_ignore_untemplated:
             return True
 
         if any(pattern.search(handler) for pattern in self.excluded_handlers):
diff --git a/tests/test_instrumentation.py b/tests/test_instrumentation.py
index 8f6eb28..be7669f 100644
--- a/tests/test_instrumentation.py
+++ b/tests/test_instrumentation.py
@@ -456,11 +456,7 @@ def test_should_respect_env_var_existence_not_exists():
 def calc_entropy(decimal_str: str):
     decimals = [int(x) for x in decimal_str]
     print(decimals)
-    entropy = 0
-    for i in range(len(decimals)):
-        if i != 0:
-            entropy += abs(decimals[i] - decimals[i - 1])
-    return entropy
+    return sum(abs(decimals[i] - decimals[i - 1]) for i in range(len(decimals)) if i != 0)
 
 
 def test_entropy():