diff --git a/scripts/build/gen_isr_tables_parser_carrays.py b/scripts/build/gen_isr_tables_parser_carrays.py
index afaff1944469588..84add9d4185b21b 100644
--- a/scripts/build/gen_isr_tables_parser_carrays.py
+++ b/scripts/build/gen_isr_tables_parser_carrays.py
@@ -188,7 +188,7 @@ def __parse_intlist(self, intlist):
     def __aligned_vt(self):
         """Returns vt with non-None entries aligned in front.
         """
-        vt = [v for v in self.__vt if not v is None] if self.__vt else []
+        vt = [v for v in self.__vt if not v is None]
         vt.extend([None] * (self.__nv- len(vt)))
         return vt
 
@@ -196,7 +196,7 @@ def __aligned_swt(self):
         """Returns swt with non-None entries aligned in front.
         Empty entries equal to the number of vt entries are inserted at the beginning.
         """
-        swt = [[] for v in self.__vt if not v is None] if self.__swt else []
+        swt = [[] for v in self.__vt if not v is None]
         swt.extend([sw for sw in self.__swt if not sw == []])
         swt.extend([[]] * (self.__nv - len(swt)))
         return swt
@@ -285,10 +285,10 @@ def __write_intr_id_table(self, fp):
         fp.write("};\n")
 
     def write_source(self, fp):
-        vt = [v for v in self.__vt if not v is None] if self.__vt else []
-        swt = [sw for sw in self.__swt if not sw == []] if self.__swt else []
+        vt_len = len([v for v in self.__vt if not v is None]) if self.__vt else 0
+        swt_len = len([sw for sw in self.__swt if not sw == []]) if self.__swt else 0
 
-        if len(vt + swt) > self.__nv:
+        if (vt_len + swt_len) > self.__nv:
             self.__log.error("Too many ISRs are defined.")
 
         fp.write(self.source_header)
diff --git a/scripts/build/gen_isr_tables_parser_local.py b/scripts/build/gen_isr_tables_parser_local.py
index d0f7d83f363a08b..16ec77ca0f8d97d 100644
--- a/scripts/build/gen_isr_tables_parser_local.py
+++ b/scripts/build/gen_isr_tables_parser_local.py
@@ -267,7 +267,7 @@ def __irq_spurious_entry(self, irq):
     def __aligned_vt(self):
         """Returns vt with non-None entries aligned in front.
         """
-        vt = [v for v in self.__vt if not v is None] if self.__vt else []
+        vt = [v for v in self.__vt if not v is None]
         vt.extend([None] * (self.__nv- len(vt)))
         return vt
 
@@ -275,7 +275,7 @@ def __aligned_swt(self):
         """Returns swt with non-None entries aligned in front.
         Empty entries equal to the number of vt entries are inserted at the beginning.
         """
-        swt = [[] for v in self.__vt if not v is None] if self.__swt else []
+        swt = [[] for v in self.__vt if not v is None]
         swt.extend([sw for sw in self.__swt if not sw == []])
         swt.extend([[]] * (self.__nv - len(swt)))
         return swt
@@ -346,10 +346,10 @@ def __write_intr_id_table(self, fp):
         fp.write("};\n")
 
     def write_source(self, fp):
-        vt = [v for v in self.__vt if not v is None] if self.__vt else []
-        swt = [sw for sw in self.__swt if not sw == []] if self.__swt else []
+        vt_len = len([v for v in self.__vt if not v is None]) if self.__vt else 0
+        swt_len = len([sw for sw in self.__swt if not sw == []]) if self.__swt else 0
 
-        if len(vt + swt) > self.__nv:
+        if (vt_len + swt_len) > self.__nv:
             self.__log.error("Too many ISRs are defined.")
 
         fp.write(self.source_header)