Refactor game_cassettebeasts.py for clarity

Refactor imports and variable initializations, and improve readability by renaming loop variables.

Author: TsunaMoo

games/game_cassettebeasts.py

@@ -1,24 +1,23 @@
+from collections.abc import Mapping, Sequence
+from datetime import datetime
+from functools import cached_property
+from io import BytesIO
+from typing import Any, Optional
+from pathlib import Path
 import json
 import math
 import os
 import shutil
 import struct
 import zlib
-import mobase
 
-from collections.abc import Mapping, Sequence
-from datetime import datetime
-from functools import cached_property
-from io import BytesIO
-from typing import Any, Optional
-from pathlib import Path
+import mobase
+from PyQt6.QtCore import QDateTime, QDir, QFile, QFileInfo
 
 from ..basic_features import BasicLocalSavegames
 from ..basic_features.basic_save_game_info import (BasicGameSaveGame,BasicGameSaveGameInfo)
 from ..basic_game import BasicGame
 
-from PyQt6.QtCore import QDateTime, QDir, QFile, QFileInfo
-
 
 def json_get_me(value: Any, path: Sequence[str | int], /, default: Any) -> Any:
     for part in path:
@@ -66,8 +65,8 @@ def fix(self, filetree: mobase.IFileTree) -> mobase.IFileTree:
 
 class CassetteBlock:
     def __init__(self):
-        compressed_size = None
-        data = None
+        compressed_size: str = "(unknown)"
+        data: str = "(unknown)"
 
 class CassetteBeastsSaveGame(BasicGameSaveGame):
     def __init__(self, filepath: Path):
@@ -85,23 +84,23 @@ def __init__(self, filepath: Path):
             info = bytearray()
             data = bytes()
             with open(filepath, 'rb') as infile:
-                magic_string = infile.read(4)
+                infile.read(4)
 
                 compression_mode, blocksize, raw_size = struct.unpack("III", infile.read(12))
 
                 num_blocks = math.ceil(raw_size / blocksize)
 
                 blocks = []
 
-                for bnum in range(num_blocks):
+                for _bnum in range(num_blocks):
                     block = CassetteBlock()
                     block.compressed_size = struct.unpack("I", infile.read(4))[0]
                     blocks.append(block)
 
                 for block in blocks:
                     block.data = infile.read(block.compressed_size)
 
-                magic_string = infile.read(4)
+                infile.read(4)
                 infile.close()
             for block in blocks:
                 data = zlib.decompress(block.data, wbits=40, bufsize=blocksize)