diff --git a/src/_pytest/python_api.py b/src/_pytest/python_api.py
index 443996b0e..724e71aa5 100644
--- a/src/_pytest/python_api.py
+++ b/src/_pytest/python_api.py
@@ -135,8 +135,8 @@ class ApproxBase:
 
 def _recursive_sequence_map(f, x):
     """Recursively map a function over a sequence of arbitary depth"""
-    seq_type = type(x)
-    if seq_type in (list, tuple):
+    if isinstance(x, (list, tuple)):
+        seq_type = type(x)
         return seq_type(_recursive_sequence_map(f, xi) for xi in x)
     else:
         return f(x)
@@ -168,7 +168,7 @@ class ApproxNumpy(ApproxBase):
             return value
 
         np_array_shape = self.expected.shape
-        approx_side_as_list = _recursive_sequence_map(
+        approx_side_as_seq = _recursive_sequence_map(
             self._approx_scalar, self.expected.tolist()
         )
 
@@ -183,7 +183,7 @@ class ApproxNumpy(ApproxBase):
         max_rel_diff = -math.inf
         different_ids = []
         for index in itertools.product(*(range(i) for i in np_array_shape)):
-            approx_value = get_value_from_nested_list(approx_side_as_list, index)
+            approx_value = get_value_from_nested_list(approx_side_as_seq, index)
             other_value = get_value_from_nested_list(other_side, index)
             if approx_value != other_value:
                 abs_diff = abs(approx_value.expected - other_value)
@@ -198,7 +198,7 @@ class ApproxNumpy(ApproxBase):
             (
                 str(index),
                 str(get_value_from_nested_list(other_side, index)),
-                str(get_value_from_nested_list(approx_side_as_list, index)),
+                str(get_value_from_nested_list(approx_side_as_seq, index)),
             )
             for index in different_ids
         ]