diff --git a/qlib/contrib/report/analysis_model/analysis_model_performance.py b/qlib/contrib/report/analysis_model/analysis_model_performance.py
index 0cdc61dda5..a2a26b9c6c 100644
--- a/qlib/contrib/report/analysis_model/analysis_model_performance.py
+++ b/qlib/contrib/report/analysis_model/analysis_model_performance.py
@@ -46,15 +46,15 @@ def __init__(self, N):
             self.cuts = {}
 
         def __call__(self, x, i):
-            l = len(x)
-            if l not in self.cuts:
-                per_group_num, remain = divmod(l, N)
+            sample_len = len(x)
+            if sample_len not in self.cuts:
+                per_group_num, remain = divmod(sample_len, N)
                 per_group_nums = np.ones(N, dtype=int) * per_group_num
                 if remain > 0:
                     per_group_nums[: remain - remain // 2] += 1
                     per_group_nums[-(remain // 2) :] += 1
-                self.cuts[l] = np.insert(np.cumsum(per_group_nums), 0, 0)
-            return x[self.cuts[l][i] : self.cuts[l][i + 1]].mean()
+                self.cuts[sample_len] = np.insert(np.cumsum(per_group_nums), 0, 0)
+            return x[self.cuts[sample_len][i] : self.cuts[sample_len][i + 1]].mean()
 
     _stratifier = _Stratifier(N)