diff --git a/bilibili_api/article.py b/bilibili_api/article.py
index 5ee96ba3..94f8a8e6 100644
--- a/bilibili_api/article.py
+++ b/bilibili_api/article.py
@@ -129,7 +129,7 @@ def __init__(self, rlid: int, credential: Union[Credential, None] = None):
             credential (Credential | None, optional): 凭据类. Defaults to None.
         """
         self.__rlid = rlid
-        self.credential = credential
+        self.credential: Credential = credential
 
     def get_rlid(self) -> int:
         return self.__rlid
diff --git a/bilibili_api/ass.py b/bilibili_api/ass.py
index 7a93d4e1..27a15336 100644
--- a/bilibili_api/ass.py
+++ b/bilibili_api/ass.py
@@ -91,7 +91,7 @@ async def make_ass_file_subtitle(
     out: Optional[str] = "test.ass",
     lan_name: Optional[str] = "中文（自动生成）",
     lan_code: Optional[str] = "ai-zh",
-    credential: Credential = Credential(),
+    credential: Optional[Credential] = None,
 ) -> None:
     """
     生成视频字幕文件
@@ -109,7 +109,7 @@ async def make_ass_file_subtitle(
 
         lan_code   (str, optional)       : 字幕语言代码，如 ”中文（自动翻译）” 和 ”中文（自动生成）“ 为 "ai-zh"
 
-        credential (Credential)          : Credential 类. 必须在此处或传入的视频 obj 中传入凭据，两者均存在则优先此处
+        credential (Credential, optional): Credential 类. 必须在此处或传入的视频 obj 中传入凭据，两者均存在则优先此处
     """
     # 目测必须得有 Credential 才能获取字幕
     if credential.has_sessdata():
diff --git a/bilibili_api/audio.py b/bilibili_api/audio.py
index ec5858da..670aadb2 100644
--- a/bilibili_api/audio.py
+++ b/bilibili_api/audio.py
@@ -29,7 +29,7 @@ def __init__(self, auid: int, credential: Union[Credential, None] = None):
 
             credential (Credential | None, optional): 凭据. Defaults to None
         """
-        self.credential = credential if credential is not None else Credential()
+        self.credential: Credential = credential if credential is not None else Credential()
         self.__auid = auid
 
     def get_auid(self) -> int:
@@ -111,7 +111,7 @@ def __init__(self, amid: int, credential: Union[Credential, None] = None):
             credential (Credential | None, optional): 凭据. Defaults to None.
         """
         self.__amid = amid
-        self.credential = credential if credential is not None else Credential()
+        self.credential: Credential = credential if credential is not None else Credential()
 
     def get_amid(self) -> int:
         return self.__amid
diff --git a/bilibili_api/audio_uploader.py b/bilibili_api/audio_uploader.py
index f7d34ee1..6261a161 100644
--- a/bilibili_api/audio_uploader.py
+++ b/bilibili_api/audio_uploader.py
@@ -516,9 +516,9 @@ def __init__(self, path: str, meta: SongMeta, credential: Credential):
             credential (Credential): 账号信息
         """
         super().__init__()
-        self.path = path
-        self.meta = meta
-        self.credential = credential
+        self.path: str = path
+        self.meta: str = meta
+        self.credential: Credential = credential
         self.__upos_file = UposFile(path)
 
     async def _preupload(self) -> dict:
diff --git a/bilibili_api/bangumi.py b/bilibili_api/bangumi.py
index b2876bc5..e039772e 100644
--- a/bilibili_api/bangumi.py
+++ b/bilibili_api/bangumi.py
@@ -1003,7 +1003,7 @@ def __init__(
         """
         if media_id == -1 and ssid == -1 and epid == -1:
             raise ValueError("需要 Media_id 或 Season_id 或 epid 中的一个 !")
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
         # 处理极端情况
         params = {}
         self.__ssid = ssid
diff --git a/bilibili_api/black_room.py b/bilibili_api/black_room.py
index a15ad643..3fcc73ad 100644
--- a/bilibili_api/black_room.py
+++ b/bilibili_api/black_room.py
@@ -198,7 +198,7 @@ def __init__(self, black_room_id: int, credential: Union[Credential, None] = Non
             credential    (Credential | None, optional): 凭据类. Defaults to None.
         """
         self.__id = black_room_id
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
 
     async def get_details(self) -> dict:
         """
@@ -238,7 +238,7 @@ def __init__(self, case_id: str, credential: Credential):
             credential (Credential)                    : 凭据类
         """
         self.case_id = case_id
-        self.credential = credential
+        self.credential: Credential = credential
 
     async def get_details(self) -> dict:
         """
diff --git a/bilibili_api/channel_series.py b/bilibili_api/channel_series.py
index fab585b3..1be72cf3 100644
--- a/bilibili_api/channel_series.py
+++ b/bilibili_api/channel_series.py
@@ -78,7 +78,7 @@ def __init__(
         self.is_new = type_.value
         self.id_ = id_
         self.owner = User(self.__uid, credential=credential)
-        self.credential = credential
+        self.credential: Credential = credential
         self.meta = None
         if not f"{type_.value}-{id_}" in channel_meta_cache.keys():
             if self.is_new:
diff --git a/bilibili_api/cheese.py b/bilibili_api/cheese.py
index ac914368..c3015872 100644
--- a/bilibili_api/cheese.py
+++ b/bilibili_api/cheese.py
@@ -61,7 +61,7 @@ def __init__(
             raise ValueError("season id 和 ep id 必须选一个")
         self.__season_id = season_id
         self.__ep_id = ep_id
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
         if self.__season_id == -1:
             # self.season_id = str(sync(self.get_meta())["season_id"])
             api = API["info"]["meta"]
@@ -150,7 +150,7 @@ def __init__(self, epid, credential: Union[Credential, None] = None):
             self.cheese = CheeseList(ep_id=self.__epid)
         else:
             self.cheese = CheeseList(season_id=meta["ssid"])
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
         if meta == None:
             api = API["info"]["meta"]
             params = {"season_id": self.cheese.get_season_id(), "ep_id": self.__epid}
diff --git a/bilibili_api/comment.py b/bilibili_api/comment.py
index cc373f7b..67fdff3a 100644
--- a/bilibili_api/comment.py
+++ b/bilibili_api/comment.py
@@ -133,7 +133,7 @@ def __init__(
         self.__oid = oid
         self.__rpid = rpid
         self.__type = type_
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
 
     def __get_data(self, status: bool) -> dict:
         """
diff --git a/bilibili_api/dynamic.py b/bilibili_api/dynamic.py
index be2f5e3b..a393002a 100644
--- a/bilibili_api/dynamic.py
+++ b/bilibili_api/dynamic.py
@@ -738,7 +738,7 @@ def __init__(
             credential (Credential | None, optional): 凭据类. Defaults to None.
         """
         self.__dynamic_id = dynamic_id
-        self.credential = credential if credential is not None else Credential()
+        self.credential: Credential = credential if credential is not None else Credential()
 
         if cache_pool.dynamic_is_opus.get(self.__dynamic_id):
             self.__opus = cache_pool.dynamic_is_opus[self.__dynamic_id]
diff --git a/bilibili_api/favorite_list.py b/bilibili_api/favorite_list.py
index 58fedcc7..71ef99fb 100644
--- a/bilibili_api/favorite_list.py
+++ b/bilibili_api/favorite_list.py
@@ -81,7 +81,7 @@ def __init__(
         """
         self.__type = type_
         self.__media_id = media_id
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
 
     def is_video_favorite_list(self) -> bool:
         """
diff --git a/bilibili_api/festival.py b/bilibili_api/festival.py
index b16fbdce..5d5a02a0 100644
--- a/bilibili_api/festival.py
+++ b/bilibili_api/festival.py
@@ -24,7 +24,7 @@ def __init__(self, fes_id: str, credential: Optional[Credential] = None) -> None
             credential (Credential, optional): 凭据类. Defaults to None.
         """
         self.fes_id = fes_id
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
 
     async def get_info(self) -> dict:
         """
diff --git a/bilibili_api/game.py b/bilibili_api/game.py
index 9f9c12c7..a0f7a89f 100644
--- a/bilibili_api/game.py
+++ b/bilibili_api/game.py
@@ -35,7 +35,7 @@ def __init__(self, game_id: int, credential: Union[None, Credential] = None):
             credential (Credential): 凭据类. Defaults to None.
         """
         self.__game_id = game_id
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
 
     def get_game_id(self) -> int:
         return self.__game_id
diff --git a/bilibili_api/live.py b/bilibili_api/live.py
index fd0a2379..1335b42d 100644
--- a/bilibili_api/live.py
+++ b/bilibili_api/live.py
@@ -118,9 +118,9 @@ def __init__(
         self.room_display_id = room_display_id
 
         if credential is None:
-            self.credential = Credential()
+            self.credential: Credential = Credential()
         else:
-            self.credential = credential
+            self.credential: Credential = credential
 
         self.__ruid = None
 
@@ -884,17 +884,17 @@ def __init__(
         """
         super().__init__()
 
-        self.credential = credential if credential is not None else Credential()
-        self.room_display_id = room_display_id
-        self.max_retry = max_retry
-        self.retry_after = retry_after
+        self.credential: Credential = credential if credential is not None else Credential()
+        self.room_display_id: int = room_display_id
+        self.max_retry: int = max_retry
+        self.retry_after: float = retry_after
         self.__room_real_id = None
         self.__status = 0
         self.__ws = None
         self.__tasks = []
         self.__debug = debug
         self.__heartbeat_timer = 60.0
-        self.err_reason = ""
+        self.err_reason: str = ""
 
         # logging
         self.logger = logging.getLogger(f"LiveDanmaku_{self.room_display_id}")
diff --git a/bilibili_api/manga.py b/bilibili_api/manga.py
index 5809a921..944da135 100644
--- a/bilibili_api/manga.py
+++ b/bilibili_api/manga.py
@@ -142,7 +142,7 @@ def __init__(self, manga_id: int, credential: Optional[Credential] = None):
         """
         credential = credential if credential else Credential()
         self.__manga_id = manga_id
-        self.credential = credential
+        self.credential: Credential = credential
         self.__info: Optional[Dict] = None
 
     def get_manga_id(self) -> int:
diff --git a/bilibili_api/opus.py b/bilibili_api/opus.py
index cd3519e3..cb33c178 100644
--- a/bilibili_api/opus.py
+++ b/bilibili_api/opus.py
@@ -43,7 +43,7 @@ def __init__(self, opus_id: int, credential: Optional[Credential] = None):
         self.__id = opus_id
         self.__is_note = False
         self.__info = None
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
 
         if cache_pool.opus_type.get(self.__id):
             self.__is_note = cache_pool.opus_is_note[self.__id]
diff --git a/bilibili_api/session.py b/bilibili_api/session.py
index 56977c40..c9e5975a 100644
--- a/bilibili_api/session.py
+++ b/bilibili_api/session.py
@@ -433,7 +433,7 @@ def __init__(self, credential: Credential, debug=False):
         self.maxSeqno = dict()
 
         # 凭证
-        self.credential = credential
+        self.credential: Credential = credential
 
         # 异步定时任务框架
         self.sched = AsyncIOScheduler(timezone="Asia/Shanghai")
diff --git a/bilibili_api/topic.py b/bilibili_api/topic.py
index e7316f54..d4463e49 100644
--- a/bilibili_api/topic.py
+++ b/bilibili_api/topic.py
@@ -82,7 +82,7 @@ def __init__(self, topic_id: int, credential: Union[Credential, None] = None):
             credential (Credential): 凭据类
         """
         self.__topic_id = topic_id
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
 
     def get_topic_id(self) -> int:
         """
diff --git a/bilibili_api/user.py b/bilibili_api/user.py
index 76d5b891..1f3b5417 100644
--- a/bilibili_api/user.py
+++ b/bilibili_api/user.py
@@ -250,7 +250,7 @@ def __init__(self, uid: int, credential: Union[Credential, None] = None):
 
         if credential is None:
             credential = Credential()
-        self.credential = credential
+        self.credential: Credential = credential
         self.__self_info = None
 
     def get_user_info_sync(self) -> dict:
diff --git a/bilibili_api/video.py b/bilibili_api/video.py
index c46da95e..24e15eb3 100644
--- a/bilibili_api/video.py
+++ b/bilibili_api/video.py
@@ -1777,7 +1777,7 @@ def __init__(
             debug      (bool, optional)             : 调试模式，将输出更详细信息. Defaults to False.
         """
         super().__init__()
-        self.credential = credential
+        self.credential: Credential = credential if credential else Credential()
         self.__video = Video(bvid, aid, credential=credential)
 
         # 智能选择在 log 中展示的 ID。
diff --git a/bilibili_api/video_tag.py b/bilibili_api/video_tag.py
index a3589e32..ceba2bce 100644
--- a/bilibili_api/video_tag.py
+++ b/bilibili_api/video_tag.py
@@ -45,7 +45,7 @@ def __init__(
         else:
             self.__tag_id = tag_id
         credential = credential if credential else Credential()
-        self.credential = credential
+        self.credential: Credential = credential
 
     def get_tag_id(self) -> int:
         return self.__tag_id
diff --git a/bilibili_api/video_uploader.py b/bilibili_api/video_uploader.py
index ebd7ea45..bf679a9d 100644
--- a/bilibili_api/video_uploader.py
+++ b/bilibili_api/video_uploader.py
@@ -728,7 +728,7 @@ def __init__(
         super().__init__()
         self.meta = meta
         self.pages = pages
-        self.credential = credential
+        self.credential: Credential = credential
         self.cover = (
             self.meta.cover
             if isinstance(self.meta, VideoMeta)
@@ -1410,7 +1410,7 @@ def __init__(
         super().__init__()
         self.bvid = bvid
         self.meta = meta
-        self.credential = credential if credential else Credential()
+        self.credential: Credential = credential if credential else Credential()
         self.cover_path = cover
         self.__old_configs = {}
         self.meta["aid"] = bvid2aid(bvid)
diff --git a/bilibili_api/vote.py b/bilibili_api/vote.py
index 66cccb52..b7e6bd52 100644
--- a/bilibili_api/vote.py
+++ b/bilibili_api/vote.py
@@ -87,7 +87,7 @@ class Vote:
         credential (Credential): 凭据类
     """
 
-    def __init__(self, vote_id: int, credential: Credential = Credential()) -> None:
+    def __init__(self, vote_id: int, credential: Optional[Credential] = None) -> None:
         """
         Args:
             vote_id (int): vote_id, 获取：https://nemo2011.github.io/bilibili-api/#/vote_id
@@ -95,7 +95,7 @@ def __init__(self, vote_id: int, credential: Credential = Credential()) -> None:
             credential (Credential): 凭据类，非必要.
         """
         self.__vote_id = vote_id
-        self.credential = credential
+        self.credential: Credential = credential if credential else Credential()
         self.title: Optional[str] = None
 
     def get_vote_id(self) -> int:
diff --git a/bilibili_api/watchroom.py b/bilibili_api/watchroom.py
index d788b55b..2d08f4e4 100644
--- a/bilibili_api/watchroom.py
+++ b/bilibili_api/watchroom.py
@@ -116,7 +116,7 @@ def __init__(self, room_id: int, credential: Credential = None):
         """
         credential = credential if credential else Credential()
         self.__room_id = room_id
-        self.credential = credential
+        self.credential: Credential = credential
         self.credential.raise_for_no_sessdata()
         self.credential.raise_for_no_bili_jct()
         if room_id in watch_room_bangumi_cache.keys():