Issue #25220: Use print(flush=True) in libregrtest

Lib/test/libregrtest/main.py

@@ -157,8 +157,8 @@ class Regrtest:
             return
         fmt = "[{1:{0}}{2}/{3}] {4}" if self.bad else "[{1:{0}}{2}] {4}"
         print(fmt.format(self.test_count_width, test_index,
-                         self.test_count, len(self.bad), test))
+                         self.test_count, len(self.bad), test),
-        sys.stdout.flush()
+              flush=True)
 
     def setup_regrtest(self):
         if self.ns.huntrleaks:
@@ -333,8 +333,7 @@ class Regrtest:
         if self.ns.verbose2 and self.bad:
             print("Re-running failed tests in verbose mode")
             for test in self.bad[:]:
-                print("Re-running test %r in verbose mode" % test)
+                print("Re-running test %r in verbose mode" % test, flush=True)
-                sys.stdout.flush()
                 try:
                     self.ns.verbose = True
                     ok = runtest(test, True, self.ns.quiet, self.ns.huntrleaks,

Lib/test/libregrtest/refleak.py

@@ -44,13 +44,12 @@ def dash_R(the_module, test, indirect_test, huntrleaks):
     alloc_deltas = [0] * repcount
 
     print("beginning", repcount, "repetitions", file=sys.stderr)
-    print(("1234567890"*(repcount//10 + 1))[:repcount], file=sys.stderr)
+    print(("1234567890"*(repcount//10 + 1))[:repcount], file=sys.stderr,
-    sys.stderr.flush()
+          flush=True)
     for i in range(repcount):
         indirect_test()
         alloc_after, rc_after = dash_R_cleanup(fs, ps, pic, zdc, abcs)
-        sys.stderr.write('.')
+        print('.', end='', flush=True)
-        sys.stderr.flush()
         if i >= nwarmup:
             rc_deltas[i] = rc_after - rc_before
             alloc_deltas[i] = alloc_after - alloc_before
@@ -74,8 +73,7 @@ def dash_R(the_module, test, indirect_test, huntrleaks):
         if checker(deltas):
             msg = '%s leaked %s %s, sum=%s' % (
                 test, deltas[nwarmup:], item_name, sum(deltas))
-            print(msg, file=sys.stderr)
+            print(msg, file=sys.stderr, flush=True)
-            sys.stderr.flush()
             with open(fname, "a") as refrep:
                 print(msg, file=refrep)
                 refrep.flush()

Lib/test/libregrtest/runtest.py

@@ -161,27 +161,23 @@ def runtest_inner(test, verbose, quiet,
             test_time = time.time() - start_time
     except support.ResourceDenied as msg:
         if not quiet:
-            print(test, "skipped --", msg)
+            print(test, "skipped --", msg, flush=True)
-            sys.stdout.flush()
         return RESOURCE_DENIED, test_time
     except unittest.SkipTest as msg:
         if not quiet:
-            print(test, "skipped --", msg)
+            print(test, "skipped --", msg, flush=True)
-            sys.stdout.flush()
         return SKIPPED, test_time
     except KeyboardInterrupt:
         raise
     except support.TestFailed as msg:
         if display_failure:
-            print("test", test, "failed --", msg, file=sys.stderr)
+            print("test", test, "failed --", msg, file=sys.stderr, flush=True)
         else:
-            print("test", test, "failed", file=sys.stderr)
+            print("test", test, "failed", file=sys.stderr, flush=True)
-        sys.stderr.flush()
         return FAILED, test_time
     except:
         msg = traceback.format_exc()
-        print("test", test, "crashed --", msg, file=sys.stderr)
+        print("test", test, "crashed --", msg, file=sys.stderr, flush=True)
-        sys.stderr.flush()
         return FAILED, test_time
     else:
         if refleak:

Lib/test/libregrtest/runtest_mp.py

@@ -70,9 +70,8 @@ def run_tests_slave(slaveargs):
     except BaseException as e:
         traceback.print_exc()
         result = CHILD_ERROR, str(e)
-    sys.stdout.flush()
     print()   # Force a newline (just in case)
-    print(json.dumps(result))
+    print(json.dumps(result), flush=True)
     sys.exit(0)
 
 
@@ -184,11 +183,9 @@ def run_tests_multiprocess(regrtest):
 
             # Copy stdout and stderr from the child process
             if stdout:
-                print(stdout)
+                print(stdout, flush=True)
             if stderr:
-                print(stderr, file=sys.stderr)
+                print(stderr, file=sys.stderr, flush=True)
-            sys.stdout.flush()
-            sys.stderr.flush()
 
             if result[0] == INTERRUPTED:
                 raise KeyboardInterrupt