diff --git a/execution.py b/execution.py
index 1e35da8db1a..5895e1031cc 100644
--- a/execution.py
+++ b/execution.py
@@ -128,59 +128,41 @@ def mark_missing():
 
 def map_node_over_list(obj, input_data_all, func, allow_interrupt=False, execution_block_cb=None, pre_execute_cb=None):
     # check if node wants the lists
-    input_is_list = False
-    if hasattr(obj, "INPUT_IS_LIST"):
-        input_is_list = obj.INPUT_IS_LIST
+    input_is_list = getattr(obj, "INPUT_IS_LIST", False)
 
     if len(input_data_all) == 0:
         max_len_input = 0
     else:
-        max_len_input = max([len(x) for x in input_data_all.values()])
+        max_len_input = max(len(x) for x in input_data_all.values())
      
     # get a slice of inputs, repeat last input when list isn't long enough
     def slice_dict(d, i):
-        d_new = dict()
-        for k,v in d.items():
-            d_new[k] = v[i if len(v) > i else -1]
-        return d_new
+        return {k: v[i if len(v) > i else -1] for k, v in d.items()}
     
     results = []
-    if input_is_list:
+    def process_inputs(inputs, index=None):
         if allow_interrupt:
             nodes.before_node_execution()
         execution_block = None
-        for k, v in input_data_all.items():
-            for input in v:
-                if isinstance(v, ExecutionBlocker):
-                    execution_block = execution_block_cb(v) if execution_block_cb is not None else v
-                    break
-
+        for k, v in inputs.items():
+            if isinstance(v, ExecutionBlocker):
+                execution_block = execution_block_cb(v) if execution_block_cb else v
+                break
         if execution_block is None:
-            if pre_execute_cb is not None:
-                pre_execute_cb(0)
-            results.append(getattr(obj, func)(**input_data_all))
+            if pre_execute_cb is not None and index is not None:
+                pre_execute_cb(index)
+            results.append(getattr(obj, func)(**inputs))
         else:
             results.append(execution_block)
+
+    if input_is_list:
+        process_inputs(input_data_all, 0)
     elif max_len_input == 0:
-        if allow_interrupt:
-            nodes.before_node_execution()
-        results.append(getattr(obj, func)())
+        process_inputs({})
     else: 
         for i in range(max_len_input):
-            if allow_interrupt:
-                nodes.before_node_execution()
             input_dict = slice_dict(input_data_all, i)
-            execution_block = None
-            for k, v in input_dict.items():
-                if isinstance(v, ExecutionBlocker):
-                    execution_block = execution_block_cb(v) if execution_block_cb is not None else v
-                    break
-            if execution_block is None:
-                if pre_execute_cb is not None:
-                    pre_execute_cb(i)
-                results.append(getattr(obj, func)(**input_dict))
-            else:
-                results.append(execution_block)
+            process_inputs(input_dict, i)
     return results
 
 def merge_result_data(results, obj):