diff --git a/ch9/circuit_breaker.py b/ch9/circuit_breaker.py
index 9bd3279..1084929 100644
--- a/ch9/circuit_breaker.py
+++ b/ch9/circuit_breaker.py
@@ -1,4 +1,6 @@
-# our version of a script provided in https://github.com/veltra/pybreaker-playground
+"""
+Our version of a script provided in https://github.com/veltra/pybreaker-playground.
+"""
 
 import pybreaker
 from datetime import datetime
@@ -11,7 +13,7 @@
 
 @breaker
 def fragile_function():
-    if not random.choice([True, False]):
+    if not random.choice([True, False]):  # nosec
         print(" / OK", end="")
     else:
         print(" / FAIL", end="")
diff --git a/ch9/retry/retry_database_connection.py b/ch9/retry/retry_database_connection.py
index 9bd6f1c..5d6921f 100644
--- a/ch9/retry/retry_database_connection.py
+++ b/ch9/retry/retry_database_connection.py
@@ -23,7 +23,7 @@ def wrapper(*args, **kwargs):
 
 @retry(attempts=3)
 def connect_to_database():
-    if random.randint(0, 1):
+    if random.randint(0, 1):  # nosec
         raise Exception("Temporary Database Error")
     return "Connected to Database"
 
diff --git a/ch9/throttling_flaskapp.py b/ch9/throttling_flaskapp.py
index 9f670d0..ff2e45a 100644
--- a/ch9/throttling_flaskapp.py
+++ b/ch9/throttling_flaskapp.py
@@ -2,8 +2,6 @@
 from flask_limiter import Limiter
 from flask_limiter.util import get_remote_address
 
-from flask import Flask
-
 app = Flask(__name__)
 limiter = Limiter(
     get_remote_address,
@@ -26,4 +24,4 @@ def more_limited_api():
 
 
 if __name__ == "__main__":
-    app.run(debug=True)
+    app.run(debug=True)  # nosec