diff --git a/gpt_engineer/ai.py b/gpt_engineer/ai.py
index 593cf36011..120be7c3fe 100644
--- a/gpt_engineer/ai.py
+++ b/gpt_engineer/ai.py
@@ -39,7 +39,7 @@ def fassistant(self, msg):
 
     def next(self, messages: list[dict[str, str]], prompt=None):
         if prompt:
-            messages = messages + [{"role": "user", "content": prompt}]
+            messages += [{"role": "user", "content": prompt}]
 
         logger.debug(f"Creating a new chat completion: {messages}")
         response = openai.ChatCompletion.create(
@@ -56,6 +56,6 @@ def next(self, messages: list[dict[str, str]], prompt=None):
             print(msg, end="")
             chat.append(msg)
         print()
-        messages = messages + [{"role": "assistant", "content": "".join(chat)}]
+        messages += [{"role": "assistant", "content": "".join(chat)}]
         logger.debug(f"Chat completion finished: {messages}")
         return messages
diff --git a/gpt_engineer/db.py b/gpt_engineer/db.py
index 3c6c12802d..13eef83c45 100644
--- a/gpt_engineer/db.py
+++ b/gpt_engineer/db.py
@@ -14,11 +14,10 @@ def __init__(self, path):
     def __getitem__(self, key):
         full_path = self.path / key
 
-        if full_path.is_file():
-            with full_path.open("r", encoding="utf-8") as f:
-                return f.read()
-        else:
+        if not full_path.is_file():
             raise KeyError(key)
+        with full_path.open("r", encoding="utf-8") as f:
+            return f.read()
 
     def __setitem__(self, key, val):
         full_path = self.path / key
diff --git a/gpt_engineer/main.py b/gpt_engineer/main.py
index 9df1f07072..34f0525c1d 100644
--- a/gpt_engineer/main.py
+++ b/gpt_engineer/main.py
@@ -33,8 +33,8 @@ def main(
     logging.basicConfig(level=logging.DEBUG if verbose else logging.INFO)
 
     input_path = Path(project_path).absolute()
-    memory_path = input_path / (run_prefix + "memory")
-    workspace_path = input_path / (run_prefix + "workspace")
+    memory_path = input_path / f"{run_prefix}memory"
+    workspace_path = input_path / f"{run_prefix}workspace"
 
     if delete_existing:
         # Delete files and subdirectories in paths
diff --git a/scripts/benchmark.py b/scripts/benchmark.py
index 2644af6c33..a909c95fca 100644
--- a/scripts/benchmark.py
+++ b/scripts/benchmark.py
@@ -23,7 +23,7 @@ def main(
     benchmarks = []
     for bench_folder in folders:
         if os.path.isdir(bench_folder):
-            print("Running benchmark for {}".format(bench_folder))
+            print(f"Running benchmark for {bench_folder}")
 
             log_path = bench_folder / "log.txt"
             log_file = open(log_path, "w")
@@ -44,7 +44,7 @@ def main(
             benchmarks.append((bench_folder, process, log_file))
 
             print("You can stream the log file by running:")
-            print("tail -f {}".format(log_path))
+            print(f"tail -f {log_path}")
             print()
 
     for bench_folder, process, file in benchmarks: