From 6e49d270571aee5b773d2316f9ed419ce3ed9e2a Mon Sep 17 00:00:00 2001
From: ViperEkura <3081035982@qq.com>
Date: Tue, 12 May 2026 11:41:45 +0800
Subject: [PATCH] =?UTF-8?q?fix:=20MultiSegmentFetcher=20=E7=A9=BA=20dict?=
 =?UTF-8?q?=20=E5=B4=A9=E6=BA=83=20+=20BaseDataset=20assert=20=E6=9B=BF?=
 =?UTF-8?q?=E6=8D=A2=E4=B8=BA=E6=98=BE=E5=BC=8F=20raise?=
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- MultiSegmentFetcher.__len__: min([]) → 加空检查返回 0
- BaseDataset.get_index: assert 替换为 RuntimeError / ValueError
- BaseDataset.__len__: assert 替换为 early return 0
---
 astrai/dataset/dataset.py | 11 ++++++++---
 astrai/dataset/storage.py |  2 ++
 2 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/astrai/dataset/dataset.py b/astrai/dataset/dataset.py
index 31920ff..6dd6099 100644
--- a/astrai/dataset/dataset.py
+++ b/astrai/dataset/dataset.py
@@ -77,9 +77,13 @@ class BaseDataset(Dataset, ABC):
         Returns:
             Tuple of (begin_idx, end_idx)
         """
-        assert self.storage is not None
+        if self.storage is None:
+            raise RuntimeError("Dataset not loaded, call load() first")
         total = len(self.storage)
-        assert total > self.window_size
+        if total <= self.window_size:
+            raise ValueError(
+                f"Data too short: {total} tokens <= window_size {self.window_size}"
+            )
 
         begin_idx = min(index * self.stride, total - 1 - self.window_size)
         end_idx = min(begin_idx + self.window_size, total - 1)
@@ -95,7 +99,8 @@ class BaseDataset(Dataset, ABC):
         raise NotImplementedError
 
     def __len__(self) -> int:
-        assert self.storage is not None
+        if self.storage is None:
+            return 0
         total = len(self.storage)
         if total <= self.window_size:
             return 0
diff --git a/astrai/dataset/storage.py b/astrai/dataset/storage.py
index d1699a6..c936ed6 100644
--- a/astrai/dataset/storage.py
+++ b/astrai/dataset/storage.py
@@ -188,6 +188,8 @@ class MultiSegmentFetcher:
 
     def __len__(self) -> int:
         """Returns the minimum length across all fetchers."""
+        if not self.multi_fetchers:
+            return 0
         len_list = [len(seg) for seg in self.multi_fetchers.values()]
         return min(len_list)