diff --git a/flang/test/Semantics/OpenACC/acc-symbols01.f90 b/flang/test/Semantics/OpenACC/acc-symbols01.f90
--- a/flang/test/Semantics/OpenACC/acc-symbols01.f90
+++ b/flang/test/Semantics/OpenACC/acc-symbols01.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/../test_symbols.py %s %flang_fc1 -fopenacc
+! RUN: %python_b %S/../test_symbols.py %s %flang_fc1 -fopenacc
 
 !DEF: /mm MainProgram
 program mm
diff --git a/flang/test/Semantics/kinds01.f90 b/flang/test/Semantics/kinds01.f90
--- a/flang/test/Semantics/kinds01.f90
+++ b/flang/test/Semantics/kinds01.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
  !DEF: /MainProgram1/jk1 ObjectEntity INTEGER(1)
  integer(kind=1) jk1
  !DEF: /MainProgram1/js1 ObjectEntity INTEGER(1)
diff --git a/flang/test/Semantics/kinds03.f90 b/flang/test/Semantics/kinds03.f90
--- a/flang/test/Semantics/kinds03.f90
+++ b/flang/test/Semantics/kinds03.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
  !DEF: /MainProgram1/ipdt DerivedType
  !DEF: /MainProgram1/ipdt/k TypeParam INTEGER(4)
  type :: ipdt(k)
diff --git a/flang/test/Semantics/omp-do-schedule03.f90 b/flang/test/Semantics/omp-do-schedule03.f90
--- a/flang/test/Semantics/omp-do-schedule03.f90
+++ b/flang/test/Semantics/omp-do-schedule03.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Schedule Clause
 ! Test that does not catch non constant integer expressions like xx - xx.
diff --git a/flang/test/Semantics/omp-do-schedule04.f90 b/flang/test/Semantics/omp-do-schedule04.f90
--- a/flang/test/Semantics/omp-do-schedule04.f90
+++ b/flang/test/Semantics/omp-do-schedule04.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Schedule Clause
 ! Test that does not catch non constant integer expressions like xx - yy.
diff --git a/flang/test/Semantics/omp-do01-positivecase.f90 b/flang/test/Semantics/omp-do01-positivecase.f90
--- a/flang/test/Semantics/omp-do01-positivecase.f90
+++ b/flang/test/Semantics/omp-do01-positivecase.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Loop Construct
 ! The loop iteration variable may not appear in a firstprivate directive.
diff --git a/flang/test/Semantics/omp-do04-positivecase.f90 b/flang/test/Semantics/omp-do04-positivecase.f90
--- a/flang/test/Semantics/omp-do04-positivecase.f90
+++ b/flang/test/Semantics/omp-do04-positivecase.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Do Loop Constructs
 
diff --git a/flang/test/Semantics/omp-do05-positivecase.f90 b/flang/test/Semantics/omp-do05-positivecase.f90
--- a/flang/test/Semantics/omp-do05-positivecase.f90
+++ b/flang/test/Semantics/omp-do05-positivecase.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Loop Construct restrictions on single directive.
 ! A positive case
diff --git a/flang/test/Semantics/omp-do06-positivecases.f90 b/flang/test/Semantics/omp-do06-positivecases.f90
--- a/flang/test/Semantics/omp-do06-positivecases.f90
+++ b/flang/test/Semantics/omp-do06-positivecases.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Loop Construct
 ! The ordered clause must be present on the loop construct if any ordered
diff --git a/flang/test/Semantics/omp-do11.f90 b/flang/test/Semantics/omp-do11.f90
--- a/flang/test/Semantics/omp-do11.f90
+++ b/flang/test/Semantics/omp-do11.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Do Loop Constructs
 
diff --git a/flang/test/Semantics/omp-do12.f90 b/flang/test/Semantics/omp-do12.f90
--- a/flang/test/Semantics/omp-do12.f90
+++ b/flang/test/Semantics/omp-do12.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Do Loop constructs.
 
diff --git a/flang/test/Semantics/omp-do14.f90 b/flang/test/Semantics/omp-do14.f90
--- a/flang/test/Semantics/omp-do14.f90
+++ b/flang/test/Semantics/omp-do14.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Do Loop constructs.
 
diff --git a/flang/test/Semantics/omp-do17.f90 b/flang/test/Semantics/omp-do17.f90
--- a/flang/test/Semantics/omp-do17.f90
+++ b/flang/test/Semantics/omp-do17.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.7.1 Do Loop constructs.
 
diff --git a/flang/test/Semantics/omp-reduction08.f90 b/flang/test/Semantics/omp-reduction08.f90
--- a/flang/test/Semantics/omp-reduction08.f90
+++ b/flang/test/Semantics/omp-reduction08.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.15.3.6 Reduction Clause Positive cases
 
diff --git a/flang/test/Semantics/omp-reduction09.f90 b/flang/test/Semantics/omp-reduction09.f90
--- a/flang/test/Semantics/omp-reduction09.f90
+++ b/flang/test/Semantics/omp-reduction09.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 ! OpenMP Version 4.5
 ! 2.15.3.6 Reduction Clause Positive cases.
 !DEF: /omp_reduction MainProgram
diff --git a/flang/test/Semantics/omp-symbol01.f90 b/flang/test/Semantics/omp-symbol01.f90
--- a/flang/test/Semantics/omp-symbol01.f90
+++ b/flang/test/Semantics/omp-symbol01.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 
 ! Test clauses that accept list.
 ! 2.1 Directive Format
diff --git a/flang/test/Semantics/omp-symbol02.f90 b/flang/test/Semantics/omp-symbol02.f90
--- a/flang/test/Semantics/omp-symbol02.f90
+++ b/flang/test/Semantics/omp-symbol02.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 
 ! 1.4.1 Structure of the OpenMP Memory Model
 
diff --git a/flang/test/Semantics/omp-symbol03.f90 b/flang/test/Semantics/omp-symbol03.f90
--- a/flang/test/Semantics/omp-symbol03.f90
+++ b/flang/test/Semantics/omp-symbol03.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 
 ! 1.4.1 Structure of the OpenMP Memory Model
 ! In the inner OpenMP region, SHARED `a` refers to the `a` in the outer OpenMP
diff --git a/flang/test/Semantics/omp-symbol04.f90 b/flang/test/Semantics/omp-symbol04.f90
--- a/flang/test/Semantics/omp-symbol04.f90
+++ b/flang/test/Semantics/omp-symbol04.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 
 ! 2.15.3 Data-Sharing Attribute Clauses
 ! Both PARALLEL and DO (worksharing) directives need to create new scope,
diff --git a/flang/test/Semantics/omp-symbol05.f90 b/flang/test/Semantics/omp-symbol05.f90
--- a/flang/test/Semantics/omp-symbol05.f90
+++ b/flang/test/Semantics/omp-symbol05.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 
 ! 2.15.2 threadprivate Directive
 ! The threadprivate directive specifies that variables are replicated,
diff --git a/flang/test/Semantics/omp-symbol06.f90 b/flang/test/Semantics/omp-symbol06.f90
--- a/flang/test/Semantics/omp-symbol06.f90
+++ b/flang/test/Semantics/omp-symbol06.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 
 ! 2.15.3 Data-Sharing Attribute Clauses
 ! A list item that specifies a given variable may not appear in more than
diff --git a/flang/test/Semantics/omp-symbol07.f90 b/flang/test/Semantics/omp-symbol07.f90
--- a/flang/test/Semantics/omp-symbol07.f90
+++ b/flang/test/Semantics/omp-symbol07.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 
 ! Generic tests
 !   1. subroutine or function calls should not be fixed for DSA or DMA
diff --git a/flang/test/Semantics/omp-symbol08.f90 b/flang/test/Semantics/omp-symbol08.f90
--- a/flang/test/Semantics/omp-symbol08.f90
+++ b/flang/test/Semantics/omp-symbol08.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1 -fopenmp
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1 -fopenmp
 
 ! 2.15.1.1 Predetermined rules for associated do-loops index variable
 !   a) The loop iteration variable(s) in the associated do-loop(s) of a do,
diff --git a/flang/test/Semantics/procinterface01.f90 b/flang/test/Semantics/procinterface01.f90
--- a/flang/test/Semantics/procinterface01.f90
+++ b/flang/test/Semantics/procinterface01.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Tests for "proc-interface" semantics.
 ! These cases are all valid.
 
diff --git a/flang/test/Semantics/symbol01.f90 b/flang/test/Semantics/symbol01.f90
--- a/flang/test/Semantics/symbol01.f90
+++ b/flang/test/Semantics/symbol01.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Test that intent-stmt and subprogram prefix and suffix are resolved.
 
 !DEF: /m Module
diff --git a/flang/test/Semantics/symbol02.f90 b/flang/test/Semantics/symbol02.f90
--- a/flang/test/Semantics/symbol02.f90
+++ b/flang/test/Semantics/symbol02.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Test host association in module subroutine and internal subroutine.
 
 !DEF: /m Module
diff --git a/flang/test/Semantics/symbol03.f90 b/flang/test/Semantics/symbol03.f90
--- a/flang/test/Semantics/symbol03.f90
+++ b/flang/test/Semantics/symbol03.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Test host association in internal subroutine of main program.
 
 !DEF: /main MainProgram
diff --git a/flang/test/Semantics/symbol05.f90 b/flang/test/Semantics/symbol05.f90
--- a/flang/test/Semantics/symbol05.f90
+++ b/flang/test/Semantics/symbol05.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Explicit and implicit entities in blocks
 
 !DEF: /s1 (Subroutine) Subprogram
diff --git a/flang/test/Semantics/symbol06.f90 b/flang/test/Semantics/symbol06.f90
--- a/flang/test/Semantics/symbol06.f90
+++ b/flang/test/Semantics/symbol06.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 !DEF: /main MainProgram
 program main
  !DEF: /main/t1 DerivedType
diff --git a/flang/test/Semantics/symbol07.f90 b/flang/test/Semantics/symbol07.f90
--- a/flang/test/Semantics/symbol07.f90
+++ b/flang/test/Semantics/symbol07.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 !DEF: /main MainProgram
 program main
  implicit complex(z)
diff --git a/flang/test/Semantics/symbol08.f90 b/flang/test/Semantics/symbol08.f90
--- a/flang/test/Semantics/symbol08.f90
+++ b/flang/test/Semantics/symbol08.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 !DEF: /main MainProgram
 program main
  !DEF: /main/x POINTER ObjectEntity REAL(4)
diff --git a/flang/test/Semantics/symbol09.f90 b/flang/test/Semantics/symbol09.f90
--- a/flang/test/Semantics/symbol09.f90
+++ b/flang/test/Semantics/symbol09.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 !DEF: /s1 (Subroutine) Subprogram
 subroutine s1
  !DEF: /s1/a ObjectEntity REAL(4)
diff --git a/flang/test/Semantics/symbol10.f90 b/flang/test/Semantics/symbol10.f90
--- a/flang/test/Semantics/symbol10.f90
+++ b/flang/test/Semantics/symbol10.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 !DEF: /m1 Module
 module m1
 contains
diff --git a/flang/test/Semantics/symbol11.f90 b/flang/test/Semantics/symbol11.f90
--- a/flang/test/Semantics/symbol11.f90
+++ b/flang/test/Semantics/symbol11.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 !DEF: /s1 (Subroutine) Subprogram
 subroutine s1
  implicit none
diff --git a/flang/test/Semantics/symbol12.f90 b/flang/test/Semantics/symbol12.f90
--- a/flang/test/Semantics/symbol12.f90
+++ b/flang/test/Semantics/symbol12.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Verify that SAVE attribute is propagated by EQUIVALENCE
 
 !DEF: /s1 (Subroutine) Subprogram
diff --git a/flang/test/Semantics/symbol13.f90 b/flang/test/Semantics/symbol13.f90
--- a/flang/test/Semantics/symbol13.f90
+++ b/flang/test/Semantics/symbol13.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Old-style "*length" specifiers (R723)
 
 !DEF: /f1 (Function) Subprogram CHARACTER(1_8,1)
diff --git a/flang/test/Semantics/symbol14.f90 b/flang/test/Semantics/symbol14.f90
--- a/flang/test/Semantics/symbol14.f90
+++ b/flang/test/Semantics/symbol14.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! "Bare" uses of type parameters and components
 
  !DEF: /MainProgram1/t1 DerivedType
diff --git a/flang/test/Semantics/symbol15.f90 b/flang/test/Semantics/symbol15.f90
--- a/flang/test/Semantics/symbol15.f90
+++ b/flang/test/Semantics/symbol15.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Forward references in pointer initializers and TBP bindings.
 
 !DEF: /m Module
diff --git a/flang/test/Semantics/symbol16.f90 b/flang/test/Semantics/symbol16.f90
--- a/flang/test/Semantics/symbol16.f90
+++ b/flang/test/Semantics/symbol16.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Statement functions
 
 !DEF: /p1 MainProgram
diff --git a/flang/test/Semantics/symbol17.f90 b/flang/test/Semantics/symbol17.f90
--- a/flang/test/Semantics/symbol17.f90
+++ b/flang/test/Semantics/symbol17.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 ! Forward references to derived types (non-error cases)
 
 !DEF: /main MainProgram
diff --git a/flang/test/Semantics/symbol18.f90 b/flang/test/Semantics/symbol18.f90
--- a/flang/test/Semantics/symbol18.f90
+++ b/flang/test/Semantics/symbol18.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 
 ! Intrinsic function in type declaration statement: type is ignored
 
diff --git a/flang/test/Semantics/symbol19.f90 b/flang/test/Semantics/symbol19.f90
--- a/flang/test/Semantics/symbol19.f90
+++ b/flang/test/Semantics/symbol19.f90
@@ -1,4 +1,4 @@
-! RUN: %python %S/test_symbols.py %s %flang_fc1
+! RUN: %python_b %S/test_symbols.py %s %flang_fc1
 
 ! Test that a procedure is only implicitly resolved as an intrinsic function
 ! (resp. subroutine) if this is a function (resp. subroutine)
diff --git a/flang/test/lit.cfg.py b/flang/test/lit.cfg.py
--- a/flang/test/lit.cfg.py
+++ b/flang/test/lit.cfg.py
@@ -32,6 +32,7 @@
 config.substitutions.append(('%PATH%', config.environment['PATH']))
 config.substitutions.append(('%llvmshlibdir', config.llvm_shlib_dir))
 config.substitutions.append(('%pluginext', config.llvm_plugin_ext))
+config.substitutions.append(('%python_b', f"{sys.executable} -B"))
 
 llvm_config.use_default_substitutions()