diff --git a/gni/protoc.py b/gni/protoc.py
index dc8920009d..d529d1c65a 100755
--- a/gni/protoc.py
+++ b/gni/protoc.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2021 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/test/benchmarks/csuite/benchmark.py b/test/benchmarks/csuite/benchmark.py
index 5d6fd0a670..99c472ca41 100755
--- a/test/benchmarks/csuite/benchmark.py
+++ b/test/benchmarks/csuite/benchmark.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 # Copyright 2018 the V8 project authors. All rights reserved.
 
 '''
diff --git a/test/benchmarks/csuite/compare-baseline.py b/test/benchmarks/csuite/compare-baseline.py
index c05e20e806..f5015124ed 100755
--- a/test/benchmarks/csuite/compare-baseline.py
+++ b/test/benchmarks/csuite/compare-baseline.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 # Copyright 2018 the V8 project authors. All rights reserved.
 
 '''
diff --git a/test/benchmarks/csuite/csuite.py b/test/benchmarks/csuite/csuite.py
index 4e7c4f35a6..70eb573606 100755
--- a/test/benchmarks/csuite/csuite.py
+++ b/test/benchmarks/csuite/csuite.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 # Copyright 2018 the V8 project authors. All rights reserved.
 '''
 C S u i t e                                         because who can remember?
diff --git a/third_party/test262-harness/src/_monkeyYaml.py b/third_party/test262-harness/src/_monkeyYaml.py
index b988c433c1..ab9b39af3e 100644
--- a/third_party/test262-harness/src/_monkeyYaml.py
+++ b/third_party/test262-harness/src/_monkeyYaml.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2014 by Sam Mikes.  All rights reserved.
 # This code is governed by the BSD license found in the LICENSE file.
 
diff --git a/third_party/test262-harness/src/parseTestRecord.py b/third_party/test262-harness/src/parseTestRecord.py
index 1c2aba80af..313ab7f3d0 100644
--- a/third_party/test262-harness/src/parseTestRecord.py
+++ b/third_party/test262-harness/src/parseTestRecord.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2011 by Google, Inc.  All rights reserved.
 # This code is governed by the BSD license found in the LICENSE file.
diff --git a/third_party/test262-harness/src/test262.py b/third_party/test262-harness/src/test262.py
index c92e5bf0cf..1ec563fc58 100755
--- a/third_party/test262-harness/src/test262.py
+++ b/third_party/test262-harness/src/test262.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2009 the Sputnik authors.  All rights reserved.
 # This code is governed by the BSD license found in the LICENSE file.
 
diff --git a/third_party/test262-harness/test/test_common.py b/third_party/test262-harness/test/test_common.py
index 4c86b0a334..4f399fd027 100644
--- a/third_party/test262-harness/test/test_common.py
+++ b/third_party/test262-harness/test/test_common.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2014 by Sam Mikes.  All rights reserved.
 # This code is governed by the BSD license found in the LICENSE file.
diff --git a/third_party/test262-harness/test/test_monkeyYaml.py b/third_party/test262-harness/test/test_monkeyYaml.py
index 428e45b6a0..1b97ea842d 100644
--- a/third_party/test262-harness/test/test_monkeyYaml.py
+++ b/third_party/test262-harness/test/test_monkeyYaml.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2014 by Sam Mikes.  All rights reserved.
 # This code is governed by the BSD license found in the LICENSE file.
diff --git a/third_party/test262-harness/test/test_parseTestRecord.py b/third_party/test262-harness/test/test_parseTestRecord.py
index 36576b57b1..869c8fb2d3 100644
--- a/third_party/test262-harness/test/test_parseTestRecord.py
+++ b/third_party/test262-harness/test/test_parseTestRecord.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2014 by Sam Mikes.  All rights reserved.
 # This code is governed by the BSD license found in the LICENSE file.
diff --git a/third_party/test262-harness/test/test_test262.py b/third_party/test262-harness/test/test_test262.py
index 8cf41d79f0..16becd192b 100644
--- a/third_party/test262-harness/test/test_test262.py
+++ b/third_party/test262-harness/test/test_test262.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2014 by Sam Mikes.  All rights reserved.
 # This code is governed by the BSD license found in the LICENSE file.
diff --git a/tools/__init__.py b/tools/__init__.py
index 3841a861c8..e1bbf0cdfc 100644
--- a/tools/__init__.py
+++ b/tools/__init__.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2018 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/adb-d8.py b/tools/adb-d8.py
index f2e67e85a6..cdb258813d 100755
--- a/tools/adb-d8.py
+++ b/tools/adb-d8.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/android-run.py b/tools/android-run.py
index 66d333a25b..ff0379869c 100755
--- a/tools/android-run.py
+++ b/tools/android-run.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
diff --git a/tools/avg.py b/tools/avg.py
index 5741acd388..b275c7f1af 100755
--- a/tools/avg.py
+++ b/tools/avg.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2018 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can
diff --git a/tools/bigint-tester.py b/tools/bigint-tester.py
index 0940369ac5..6cc8d98cf4 100755
--- a/tools/bigint-tester.py
+++ b/tools/bigint-tester.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/builtins-pgo/combine_hints.py b/tools/builtins-pgo/combine_hints.py
index 18c45edd96..25412e9749 100755
--- a/tools/builtins-pgo/combine_hints.py
+++ b/tools/builtins-pgo/combine_hints.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2022 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can
diff --git a/tools/builtins-pgo/generate.py b/tools/builtins-pgo/generate.py
index be5b12935b..a77b7bb9a6 100755
--- a/tools/builtins-pgo/generate.py
+++ b/tools/builtins-pgo/generate.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2022 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can
diff --git a/tools/builtins-pgo/get_hints.py b/tools/builtins-pgo/get_hints.py
index 3e53ad9d6c..b717dc05ca 100755
--- a/tools/builtins-pgo/get_hints.py
+++ b/tools/builtins-pgo/get_hints.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2022 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can
diff --git a/tools/callstats.py b/tools/callstats.py
index 1b76d0c166..dbeb1c9721 100755
--- a/tools/callstats.py
+++ b/tools/callstats.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/clusterfuzz/js_fuzzer/tools/fuzz_one.py b/tools/clusterfuzz/js_fuzzer/tools/fuzz_one.py
index 28646d4c8f..c3df79ec27 100644
--- a/tools/clusterfuzz/js_fuzzer/tools/fuzz_one.py
+++ b/tools/clusterfuzz/js_fuzzer/tools/fuzz_one.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2020 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/clusterfuzz/js_fuzzer/tools/minimize.py b/tools/clusterfuzz/js_fuzzer/tools/minimize.py
index 8729b2acac..be864d5463 100644
--- a/tools/clusterfuzz/js_fuzzer/tools/minimize.py
+++ b/tools/clusterfuzz/js_fuzzer/tools/minimize.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2020 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/clusterfuzz/js_fuzzer/tools/run_one.py b/tools/clusterfuzz/js_fuzzer/tools/run_one.py
index 7886c30b95..4719fe0e72 100644
--- a/tools/clusterfuzz/js_fuzzer/tools/run_one.py
+++ b/tools/clusterfuzz/js_fuzzer/tools/run_one.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2020 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/clusterfuzz/js_fuzzer/tools/workbench.py b/tools/clusterfuzz/js_fuzzer/tools/workbench.py
index ee371f5482..5a4fc0a19c 100644
--- a/tools/clusterfuzz/js_fuzzer/tools/workbench.py
+++ b/tools/clusterfuzz/js_fuzzer/tools/workbench.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2020 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/dev/gen-tags.py b/tools/dev/gen-tags.py
index a478ee3f56..5bed28e3fa 100755
--- a/tools/dev/gen-tags.py
+++ b/tools/dev/gen-tags.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/dev/v8gen.py b/tools/dev/v8gen.py
index c6ba1d2174..6874c57155 100755
--- a/tools/dev/v8gen.py
+++ b/tools/dev/v8gen.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/disasm.py b/tools/disasm.py
index cd27faa506..71fff96c68 100644
--- a/tools/disasm.py
+++ b/tools/disasm.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2011 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
diff --git a/tools/dump-cpp.py b/tools/dump-cpp.py
index 58c08c8a7f..27b59b19a0 100644
--- a/tools/dump-cpp.py
+++ b/tools/dump-cpp.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/eval_gc_nvp.py b/tools/eval_gc_nvp.py
index 222ebef7d3..dea2da46c3 100755
--- a/tools/eval_gc_nvp.py
+++ b/tools/eval_gc_nvp.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/find-commit-for-patch.py b/tools/find-commit-for-patch.py
index cca1f40d55..a1995669b6 100755
--- a/tools/find-commit-for-patch.py
+++ b/tools/find-commit-for-patch.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/gc-nvp-to-csv.py b/tools/gc-nvp-to-csv.py
index b3ad374185..f8590717bb 100755
--- a/tools/gc-nvp-to-csv.py
+++ b/tools/gc-nvp-to-csv.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/gc-nvp-trace-processor.py b/tools/gc-nvp-trace-processor.py
index 75d50b1cda..f5f8be4c84 100755
--- a/tools/gc-nvp-trace-processor.py
+++ b/tools/gc-nvp-trace-processor.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2010 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
diff --git a/tools/gen-inlining-tests.py b/tools/gen-inlining-tests.py
index 484faa10e8..97323a9870 100644
--- a/tools/gen-inlining-tests.py
+++ b/tools/gen-inlining-tests.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/gen-keywords-gen-h.py b/tools/gen-keywords-gen-h.py
index 97c91ee289..a61f51aab5 100755
--- a/tools/gen-keywords-gen-h.py
+++ b/tools/gen-keywords-gen-h.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2018 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/gen-postmortem-metadata.py b/tools/gen-postmortem-metadata.py
index 43fe38c03d..4ffa36560e 100644
--- a/tools/gen-postmortem-metadata.py
+++ b/tools/gen-postmortem-metadata.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
diff --git a/tools/gen-v8-gn.py b/tools/gen-v8-gn.py
index 21d9f3a3a2..06f352c163 100755
--- a/tools/gen-v8-gn.py
+++ b/tools/gen-v8-gn.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2021 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/generate-builtins-tests.py b/tools/generate-builtins-tests.py
index 3abe750b53..c4286e958a 100755
--- a/tools/generate-builtins-tests.py
+++ b/tools/generate-builtins-tests.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/generate-header-include-checks.py b/tools/generate-header-include-checks.py
index fd95b83004..c52b0f9663 100755
--- a/tools/generate-header-include-checks.py
+++ b/tools/generate-header-include-checks.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # vim:fenc=utf-8:shiftwidth=2
 
 # Copyright 2018 the V8 project authors. All rights reserved.
diff --git a/tools/generate_shim_headers/generate_shim_headers.py b/tools/generate_shim_headers/generate_shim_headers.py
index d0e6d069de..647d30faa3 100755
--- a/tools/generate_shim_headers/generate_shim_headers.py
+++ b/tools/generate_shim_headers/generate_shim_headers.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2013 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
diff --git a/tools/locs.py b/tools/locs.py
index bd1609dc7f..f8940c05e6 100755
--- a/tools/locs.py
+++ b/tools/locs.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2018 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/mb/PRESUBMIT.py b/tools/mb/PRESUBMIT.py
index 150de90e88..bae713bc25 100644
--- a/tools/mb/PRESUBMIT.py
+++ b/tools/mb/PRESUBMIT.py
@@ -18,15 +18,17 @@ def _CommonChecks(input_api, output_api):
   # Run the MB unittests.
   results.extend(
       input_api.canned_checks.RunUnitTestsInDirectory(input_api, output_api,
-                                                      '.', [r'^.+_test\.py$']))
+                                                      '.', [r'^.+_test\.py$'],
+                                                      run_on_python2=False))
 
   # Validate the format of the mb_config.pyl file.
-  cmd = [input_api.python_executable, 'mb.py', 'validate']
+  cmd = [input_api.python3_executable, 'mb.py', 'validate']
   kwargs = {'cwd': input_api.PresubmitLocalPath()}
   results.extend(input_api.RunTests([
       input_api.Command(name='mb_validate',
                         cmd=cmd, kwargs=kwargs,
-                        message=output_api.PresubmitError)]))
+                        message=output_api.PresubmitError,
+                        python3=True)]))
 
   is_mb_config = (lambda filepath: 'mb_config.pyl' in filepath.LocalPath())
   results.extend(
diff --git a/tools/mb/mb.py b/tools/mb/mb.py
index 1ba74b747b..f42b52bedb 100755
--- a/tools/mb/mb.py
+++ b/tools/mb/mb.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -66,9 +66,9 @@ def _v8_builder_fallback(builder, builder_group):
   elif builder.endswith(' builder'):
     builders.append(builder[:-len(' builder')])
 
-  for builder in builders:
-    if builder in builder_group:
-      return builder_group[builder]
+  for b in builders:
+    if b in builder_group:
+      return builder_group[b]
   return None
 
 
@@ -77,7 +77,7 @@ def main(args):
   return mbw.Main(args)
 
 
-class MetaBuildWrapper(object):
+class MetaBuildWrapper():
   def __init__(self):
     self.chromium_src_dir = CHROMIUM_SRC_DIR
     self.default_config = os.path.join(self.chromium_src_dir, 'infra', 'mb',
@@ -562,7 +562,7 @@ class MetaBuildWrapper(object):
       contents = ast.literal_eval(self.ReadFile(self.args.config_file))
     except SyntaxError as e:
       raise MBErr('Failed to parse config file "%s": %s' %
-                 (self.args.config_file, e))
+                 (self.args.config_file, e)) from e
 
     self.configs = contents['configs']
     self.luci_tryservers = contents.get('luci_tryservers', {})
@@ -587,8 +587,8 @@ class MetaBuildWrapper(object):
               ', '.join(duplicates))
         isolate_maps.update(isolate_map)
       except SyntaxError as e:
-        raise MBErr(
-            'Failed to parse isolate map file "%s": %s' % (isolate_map, e))
+        raise MBErr('Failed to parse isolate map file "%s": %s' %
+                    (isolate_map, e)) from e
     return isolate_maps
 
   def ConfigFromArgs(self):
@@ -1071,7 +1071,7 @@ class MetaBuildWrapper(object):
                      force_verbose=force_verbose)
     except Exception as e:
       raise MBErr('Error %s writing to the output path "%s"' %
-                 (e, path))
+                 (e, path)) from e
 
   def CheckCompile(self, builder_group, builder):
     url_template = self.args.url_template + '/{builder}/builds/_all?as_text=1'
@@ -1089,7 +1089,7 @@ class MetaBuildWrapper(object):
     if not successes:
       return "no successful builds"
     build = builds[str(successes[0])]
-    step_names = set([step["name"] for step in build["steps"]])
+    step_names = {step["name"] for step in build["steps"]}
     compile_indicators = set(["compile", "compile (with patch)", "analyze"])
     if compile_indicators & step_names:
       return "compiles"
diff --git a/tools/mb/mb_test.py b/tools/mb/mb_test.py
index fb59c4aa29..0f03adba82 100755
--- a/tools/mb/mb_test.py
+++ b/tools/mb/mb_test.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Copyright 2015 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -6,7 +6,7 @@
 """Tests for mb.py."""
 
 import json
-import StringIO
+import io
 import os
 import sys
 import unittest
@@ -17,7 +17,7 @@ import mb
 class FakeMBW(mb.MetaBuildWrapper):
 
   def __init__(self, win32=False):
-    super(FakeMBW, self).__init__()
+    super().__init__()
 
     # Override vars for test portability.
     if win32:
@@ -85,14 +85,14 @@ class FakeMBW(mb.MetaBuildWrapper):
   def RemoveFile(self, path):
     del self.files[path]
 
-  def RemoveDirectory(self, path):
-    self.rmdirs.append(path)
-    files_to_delete = [f for f in self.files if f.startswith(path)]
+  def RemoveDirectory(self, abs_path):
+    self.rmdirs.append(abs_path)
+    files_to_delete = [f for f in self.files if f.startswith(abs_path)]
     for f in files_to_delete:
       self.files[f] = None
 
 
-class FakeFile(object):
+class FakeFile():
 
   def __init__(self, files):
     self.name = '/tmp/file'
@@ -592,7 +592,7 @@ class UnitTest(unittest.TestCase):
   def test_help(self):
     orig_stdout = sys.stdout
     try:
-      sys.stdout = StringIO.StringIO()
+      sys.stdout = io.StringIO()
       self.assertRaises(SystemExit, self.check, ['-h'])
       self.assertRaises(SystemExit, self.check, ['help'])
       self.assertRaises(SystemExit, self.check, ['help', 'gen'])
diff --git a/tools/objdump-v8 b/tools/objdump-v8
index dc7310a5f8..53f0af4e69 100755
--- a/tools/objdump-v8
+++ b/tools/objdump-v8
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
diff --git a/tools/perf-compare.py b/tools/perf-compare.py
index 744f6aae97..31f91df805 100755
--- a/tools/perf-compare.py
+++ b/tools/perf-compare.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/profiling/ll_prof.py b/tools/profiling/ll_prof.py
index 44998743b4..998965694c 100755
--- a/tools/profiling/ll_prof.py
+++ b/tools/profiling/ll_prof.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
diff --git a/tools/regexp-sequences.py b/tools/regexp-sequences.py
index 9f920dd0f0..295f74acfb 100755
--- a/tools/regexp-sequences.py
+++ b/tools/regexp-sequences.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2019 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/release/auto_roll.py b/tools/release/auto_roll.py
index 4585b27f1f..cb72022310 100755
--- a/tools/release/auto_roll.py
+++ b/tools/release/auto_roll.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/release/filter_build_files.py b/tools/release/filter_build_files.py
index 65312b4b85..68c60efc87 100755
--- a/tools/release/filter_build_files.py
+++ b/tools/release/filter_build_files.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/release/mergeinfo.py b/tools/release/mergeinfo.py
index 5a82cbf7ce..d824f4738a 100755
--- a/tools/release/mergeinfo.py
+++ b/tools/release/mergeinfo.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/release/test_mergeinfo.py b/tools/release/test_mergeinfo.py
index 9404542ef6..8c95de1116 100755
--- a/tools/release/test_mergeinfo.py
+++ b/tools/release/test_mergeinfo.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2015 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/run-clang-tidy.py b/tools/run-clang-tidy.py
index aee1b40bef..b5de57ac3c 100755
--- a/tools/run-clang-tidy.py
+++ b/tools/run-clang-tidy.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2018 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/run-num-fuzzer.py b/tools/run-num-fuzzer.py
index 49e432998d..699d33cbd2 100755
--- a/tools/run-num-fuzzer.py
+++ b/tools/run-num-fuzzer.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2018 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/run-tests.py b/tools/run-tests.py
index d22c7303af..4ddf97f4e7 100755
--- a/tools/run-tests.py
+++ b/tools/run-tests.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/run-wasm-api-tests.py b/tools/run-wasm-api-tests.py
index ff37c8a465..92df8ad0c2 100755
--- a/tools/run-wasm-api-tests.py
+++ b/tools/run-wasm-api-tests.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2019 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/sanitizers/sancov_formatter.py b/tools/sanitizers/sancov_formatter.py
index c95ff821c3..126acbd8f8 100755
--- a/tools/sanitizers/sancov_formatter.py
+++ b/tools/sanitizers/sancov_formatter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/sanitizers/sancov_merger.py b/tools/sanitizers/sancov_merger.py
index 6fd2eb2555..94ce24bfb4 100755
--- a/tools/sanitizers/sancov_merger.py
+++ b/tools/sanitizers/sancov_merger.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/sanitizers/sanitize_pcs.py b/tools/sanitizers/sanitize_pcs.py
index a1e3a1df2e..e23f4f2cd6 100755
--- a/tools/sanitizers/sanitize_pcs.py
+++ b/tools/sanitizers/sanitize_pcs.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2016 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/snapshot/asm_to_inline_asm.py b/tools/snapshot/asm_to_inline_asm.py
index e49c961bb7..ce57d8fc0b 100644
--- a/tools/snapshot/asm_to_inline_asm.py
+++ b/tools/snapshot/asm_to_inline_asm.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2018 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
diff --git a/tools/stats-viewer.py b/tools/stats-viewer.py
index dd9d2c20bf..535402a452 100755
--- a/tools/stats-viewer.py
+++ b/tools/stats-viewer.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 #
 # Copyright 2008 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
diff --git a/tools/testrunner/local/fake_testsuite/testcfg.py b/tools/testrunner/local/fake_testsuite/testcfg.py
index 7dc5d7068f..eced9ce8fc 100644
--- a/tools/testrunner/local/fake_testsuite/testcfg.py
+++ b/tools/testrunner/local/fake_testsuite/testcfg.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2019 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/try_perf.py b/tools/try_perf.py
index 55ae8b4412..24c481d21c 100755
--- a/tools/try_perf.py
+++ b/tools/try_perf.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/unittests/testdata/d8_mocked1.py b/tools/unittests/testdata/d8_mocked1.py
index ff330af8c4..ea0377c559 100644
--- a/tools/unittests/testdata/d8_mocked1.py
+++ b/tools/unittests/testdata/d8_mocked1.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/unittests/testdata/d8_mocked2.py b/tools/unittests/testdata/d8_mocked2.py
index 36304628aa..c071e15a37 100644
--- a/tools/unittests/testdata/d8_mocked2.py
+++ b/tools/unittests/testdata/d8_mocked2.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/unittests/testdata/results_processor.py b/tools/unittests/testdata/results_processor.py
index d8c5ad9448..c2e3c8d0ed 100644
--- a/tools/unittests/testdata/results_processor.py
+++ b/tools/unittests/testdata/results_processor.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2017 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/v8windbg/copy-prereqs.py b/tools/v8windbg/copy-prereqs.py
index c13efe6582..810535c4a3 100644
--- a/tools/v8windbg/copy-prereqs.py
+++ b/tools/v8windbg/copy-prereqs.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Copyright 2020 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
diff --git a/tools/wasm-compilation-hints/inject-compilation-hints.py b/tools/wasm-compilation-hints/inject-compilation-hints.py
index fd4b65b8ff..b04bf2cd80 100755
--- a/tools/wasm-compilation-hints/inject-compilation-hints.py
+++ b/tools/wasm-compilation-hints/inject-compilation-hints.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2019 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be found
diff --git a/tools/wasm-compilation-hints/wasm-objdump-compilation-hints.py b/tools/wasm-compilation-hints/wasm-objdump-compilation-hints.py
index 9077f97f70..a1dd8e4d39 100755
--- a/tools/wasm-compilation-hints/wasm-objdump-compilation-hints.py
+++ b/tools/wasm-compilation-hints/wasm-objdump-compilation-hints.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2019 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be found
diff --git a/tools/wasm-compilation-hints/wasm.py b/tools/wasm-compilation-hints/wasm.py
index ae3d0841e8..bbd3e5bbbe 100644
--- a/tools/wasm-compilation-hints/wasm.py
+++ b/tools/wasm-compilation-hints/wasm.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Copyright 2019 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be found