diff --git a/Lib/difflib.py b/Lib/difflib.py
index fe94cc47ab5..f0bfcc50702 100644
--- a/Lib/difflib.py
+++ b/Lib/difflib.py
@@ -1,5 +1,3 @@
-#! /usr/bin/env python3
-
 """
 Module difflib -- helpers for computing deltas between objects.
 
diff --git a/Lib/http/cookies.py b/Lib/http/cookies.py
index dc3c74a8db2..24da5f490c2 100644
--- a/Lib/http/cookies.py
+++ b/Lib/http/cookies.py
@@ -1,6 +1,3 @@
-#!/usr/bin/env python3
-#
-
 ####
 # Copyright 2000 by Timothy O'Malley <timo@alum.mit.edu>
 #
diff --git a/Lib/lib2to3/tests/data/different_encoding.py b/Lib/lib2to3/tests/data/different_encoding.py
old mode 100644
new mode 100755
diff --git a/Lib/lib2to3/tests/data/false_encoding.py b/Lib/lib2to3/tests/data/false_encoding.py
old mode 100644
new mode 100755
diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index d59dae85cdf..3b64c2ed0da 100644
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -1,5 +1,3 @@
-#! /usr/bin/env python3
-
 """Read/write support for Maildir, mbox, MH, Babyl, and MMDF mailboxes."""
 
 # Notes for authors of new mailbox subclasses:
diff --git a/Lib/smtplib.py b/Lib/smtplib.py
old mode 100644
new mode 100755
diff --git a/Lib/tarfile.py b/Lib/tarfile.py
old mode 100644
new mode 100755
diff --git a/Lib/test/crashers/recursive_call.py b/Lib/test/crashers/recursive_call.py
old mode 100644
new mode 100755
diff --git a/Lib/test/curses_tests.py b/Lib/test/curses_tests.py
old mode 100644
new mode 100755
diff --git a/Lib/test/multibytecodec_support.py b/Lib/test/multibytecodec_support.py
index 24003239675..14fea3ef7d3 100644
--- a/Lib/test/multibytecodec_support.py
+++ b/Lib/test/multibytecodec_support.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # multibytecodec_support.py
 #   Common Unittest Routines for CJK codecs
diff --git a/Lib/test/test___future__.py b/Lib/test/test___future__.py
index 9ae4ce40ad4..6f73c7fddfd 100644
--- a/Lib/test/test___future__.py
+++ b/Lib/test/test___future__.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 import unittest
 from test import support
 import __future__
diff --git a/Lib/test/test_array.py b/Lib/test/test_array.py
old mode 100755
new mode 100644
index e1362b20e5a..d68284f9195
--- a/Lib/test/test_array.py
+++ b/Lib/test/test_array.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 """Test the arraymodule.
    Roger E. Masse
 """
diff --git a/Lib/test/test_binhex.py b/Lib/test/test_binhex.py
old mode 100755
new mode 100644
index a807bca6393..9d4c85afaa6
--- a/Lib/test/test_binhex.py
+++ b/Lib/test/test_binhex.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 """Test script for the binhex C module
 
    Uses the mechanism of the python binhex module
diff --git a/Lib/test/test_bz2.py b/Lib/test/test_bz2.py
index 961053d0296..c8c93513d89 100644
--- a/Lib/test/test_bz2.py
+++ b/Lib/test/test_bz2.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 from test import support
 from test.support import TESTFN, bigmemtest, _4G
 
diff --git a/Lib/test/test_cmd.py b/Lib/test/test_cmd.py
index 66185358237..e9a0211682a 100644
--- a/Lib/test/test_cmd.py
+++ b/Lib/test/test_cmd.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 """
 Test script for the 'cmd' module
 Original by Michael Schneider
diff --git a/Lib/test/test_codecencodings_cn.py b/Lib/test/test_codecencodings_cn.py
index b08c5fcb1a7..60e69eb7626 100644
--- a/Lib/test/test_codecencodings_cn.py
+++ b/Lib/test/test_codecencodings_cn.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecencodings_cn.py
 #   Codec encoding tests for PRC encodings.
diff --git a/Lib/test/test_codecencodings_hk.py b/Lib/test/test_codecencodings_hk.py
index 31363f4bea8..25c05b6048f 100644
--- a/Lib/test/test_codecencodings_hk.py
+++ b/Lib/test/test_codecencodings_hk.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecencodings_hk.py
 #   Codec encoding tests for HongKong encodings.
diff --git a/Lib/test/test_codecencodings_iso2022.py b/Lib/test/test_codecencodings_iso2022.py
index e4b2f306d5d..87768646fe4 100644
--- a/Lib/test/test_codecencodings_iso2022.py
+++ b/Lib/test/test_codecencodings_iso2022.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-#
 # Codec encoding tests for ISO 2022 encodings.
 
 from test import support
diff --git a/Lib/test/test_codecencodings_jp.py b/Lib/test/test_codecencodings_jp.py
index 30c9e195f31..4091948b9b8 100644
--- a/Lib/test/test_codecencodings_jp.py
+++ b/Lib/test/test_codecencodings_jp.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecencodings_jp.py
 #   Codec encoding tests for Japanese encodings.
diff --git a/Lib/test/test_codecencodings_kr.py b/Lib/test/test_codecencodings_kr.py
index 4dd60499c87..cd7696acaa3 100644
--- a/Lib/test/test_codecencodings_kr.py
+++ b/Lib/test/test_codecencodings_kr.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecencodings_kr.py
 #   Codec encoding tests for ROK encodings.
diff --git a/Lib/test/test_codecencodings_tw.py b/Lib/test/test_codecencodings_tw.py
index 96245b74ed3..ea6e1c16239 100644
--- a/Lib/test/test_codecencodings_tw.py
+++ b/Lib/test/test_codecencodings_tw.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecencodings_tw.py
 #   Codec encoding tests for ROC encodings.
diff --git a/Lib/test/test_codecmaps_cn.py b/Lib/test/test_codecmaps_cn.py
index 1a761cffc76..76632a24352 100644
--- a/Lib/test/test_codecmaps_cn.py
+++ b/Lib/test/test_codecmaps_cn.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecmaps_cn.py
 #   Codec mapping tests for PRC encodings
diff --git a/Lib/test/test_codecmaps_hk.py b/Lib/test/test_codecmaps_hk.py
index 5f4e7c7e020..278ae2ffeb3 100644
--- a/Lib/test/test_codecmaps_hk.py
+++ b/Lib/test/test_codecmaps_hk.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecmaps_hk.py
 #   Codec mapping tests for HongKong encodings
diff --git a/Lib/test/test_codecmaps_jp.py b/Lib/test/test_codecmaps_jp.py
index 1fdbf634e3a..fa93f12f5a3 100644
--- a/Lib/test/test_codecmaps_jp.py
+++ b/Lib/test/test_codecmaps_jp.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecmaps_jp.py
 #   Codec mapping tests for Japanese encodings
diff --git a/Lib/test/test_codecmaps_kr.py b/Lib/test/test_codecmaps_kr.py
index 03564025ed2..e0bf7169948 100644
--- a/Lib/test/test_codecmaps_kr.py
+++ b/Lib/test/test_codecmaps_kr.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecmaps_kr.py
 #   Codec mapping tests for ROK encodings
diff --git a/Lib/test/test_codecmaps_tw.py b/Lib/test/test_codecmaps_tw.py
index 44467e378a7..4d270804f09 100644
--- a/Lib/test/test_codecmaps_tw.py
+++ b/Lib/test/test_codecmaps_tw.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_codecmaps_tw.py
 #   Codec mapping tests for ROC encodings
diff --git a/Lib/test/test_dbm.py b/Lib/test/test_dbm.py
index 243a0af1031..d11d924b308 100644
--- a/Lib/test/test_dbm.py
+++ b/Lib/test/test_dbm.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 """Test script for the dbm.open function based on testdumbdbm.py"""
 
 import os
diff --git a/Lib/test/test_dbm_dumb.py b/Lib/test/test_dbm_dumb.py
index 208bc4c3823..4f03ae7e585 100644
--- a/Lib/test/test_dbm_dumb.py
+++ b/Lib/test/test_dbm_dumb.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 """Test script for the dumbdbm module
    Original by Roger E. Masse
 """
diff --git a/Lib/test/test_eof.py b/Lib/test/test_eof.py
index fb4ac9a639f..52e7932c1ab 100644
--- a/Lib/test/test_eof.py
+++ b/Lib/test/test_eof.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 """test script for a few new invalid token catches"""
 
 import unittest
diff --git a/Lib/test/test_errno.py b/Lib/test/test_errno.py
old mode 100755
new mode 100644
index f414a87796f..058dcb9a235
--- a/Lib/test/test_errno.py
+++ b/Lib/test/test_errno.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 """Test the errno module
    Roger E. Masse
 """
diff --git a/Lib/test/test_gzip.py b/Lib/test/test_gzip.py
index 5eac9217b22..c94d54e02e6 100755
--- a/Lib/test/test_gzip.py
+++ b/Lib/test/test_gzip.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 """Test script for the gzip module.
 """
 
diff --git a/Lib/test/test_keywordonlyarg.py b/Lib/test/test_keywordonlyarg.py
index 0503a7fc6a4..6c2ff00362b 100644
--- a/Lib/test/test_keywordonlyarg.py
+++ b/Lib/test/test_keywordonlyarg.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 """Unit tests for the keyword only argument specified in PEP 3102."""
 
 __author__ = "Jiwon Seo"
diff --git a/Lib/test/test_logging.py b/Lib/test/test_logging.py
index 814f68cc154..f34172a371d 100644
--- a/Lib/test/test_logging.py
+++ b/Lib/test/test_logging.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-#
 # Copyright 2001-2013 by Vinay Sajip. All Rights Reserved.
 #
 # Permission to use, copy, modify, and distribute this software and its
diff --git a/Lib/test/test_marshal.py b/Lib/test/test_marshal.py
index af7a9594872..0b1413715d5 100644
--- a/Lib/test/test_marshal.py
+++ b/Lib/test/test_marshal.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 from test import support
 import array
 import io
diff --git a/Lib/test/test_multibytecodec.py b/Lib/test/test_multibytecodec.py
index feb7bd595a2..6889184cce6 100644
--- a/Lib/test/test_multibytecodec.py
+++ b/Lib/test/test_multibytecodec.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 #
 # test_multibytecodec.py
 #   Unit test for multibytecodec itself
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index d20a57698d2..aa66db4b7e6 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 #
 # Unit tests for the multiprocessing package
 #
diff --git a/Lib/test/test_popen.py b/Lib/test/test_popen.py
index accf187b54d..225e41f86b4 100644
--- a/Lib/test/test_popen.py
+++ b/Lib/test/test_popen.py
@@ -1,4 +1,3 @@
-#! /usr/bin/env python3
 """Basic tests for os.popen()
 
   Particularly useful for platforms that fake popen.
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index d363a6a1d15..a475207fbd1 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import unittest
 import random
 import time
diff --git a/Lib/test/test_sched.py b/Lib/test/test_sched.py
index 070886d1ea5..79fa7d3e3dd 100644
--- a/Lib/test/test_sched.py
+++ b/Lib/test/test_sched.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 import queue
 import sched
 import time
diff --git a/Lib/test/test_smtpnet.py b/Lib/test/test_smtpnet.py
index 86224ef2e45..e97cf363bb6 100644
--- a/Lib/test/test_smtpnet.py
+++ b/Lib/test/test_smtpnet.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import unittest
 from test import support
 import smtplib
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index ce3c16ca821..d6e8389eb48 100644
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import unittest
 from test import support
 from unittest.case import _ExpectedFailure
diff --git a/Lib/test/test_support.py b/Lib/test/test_support.py
index 4edb1a8e01c..5913044877c 100644
--- a/Lib/test/test_support.py
+++ b/Lib/test/test_support.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python
-
 import importlib
 import shutil
 import sys
diff --git a/Lib/test/test_tcl.py b/Lib/test/test_tcl.py
index 5a2b69a0bef..ad17ee95d3c 100644
--- a/Lib/test/test_tcl.py
+++ b/Lib/test/test_tcl.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import unittest
 import sys
 import os
diff --git a/Lib/test/test_urllib2_localnet.py b/Lib/test/test_urllib2_localnet.py
index 9112e5062b1..31c638fc4e8 100644
--- a/Lib/test/test_urllib2_localnet.py
+++ b/Lib/test/test_urllib2_localnet.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import os
 import email
 import urllib.parse
diff --git a/Lib/test/test_urllib2net.py b/Lib/test/test_urllib2net.py
index 7f3c93adaa5..a4c16224fb4 100644
--- a/Lib/test/test_urllib2net.py
+++ b/Lib/test/test_urllib2net.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import unittest
 from test import support
 from test.test_urllib2 import sanepathname2url
diff --git a/Lib/test/test_urllibnet.py b/Lib/test/test_urllibnet.py
index 9aa16b4c9ce..4e0b7bde9ad 100644
--- a/Lib/test/test_urllibnet.py
+++ b/Lib/test/test_urllibnet.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import unittest
 from test import support
 
diff --git a/Lib/test/test_urlparse.py b/Lib/test/test_urlparse.py
old mode 100755
new mode 100644
index 378a427bc56..9d695da9a12
--- a/Lib/test/test_urlparse.py
+++ b/Lib/test/test_urlparse.py
@@ -1,5 +1,3 @@
-#! /usr/bin/env python3
-
 from test import support
 import unittest
 import urllib.parse
diff --git a/Lib/test/test_userstring.py b/Lib/test/test_userstring.py
old mode 100755
new mode 100644
index 71fcac25e13..34c629cb764
--- a/Lib/test/test_userstring.py
+++ b/Lib/test/test_userstring.py
@@ -1,4 +1,3 @@
-#!/usr/bin/env python3
 # UserString is a wrapper around the native builtin string type.
 # UserString instances should behave similar to builtin string objects.
 
diff --git a/Lib/test/test_with.py b/Lib/test/test_with.py
index e8cc8c056ec..7068a809702 100644
--- a/Lib/test/test_with.py
+++ b/Lib/test/test_with.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 """Unit tests for the with statement specified in PEP 343."""
 
 
diff --git a/Lib/test/test_xmlrpc_net.py b/Lib/test/test_xmlrpc_net.py
index 4c6f1ec4e95..77f66ea57bd 100644
--- a/Lib/test/test_xmlrpc_net.py
+++ b/Lib/test/test_xmlrpc_net.py
@@ -1,5 +1,3 @@
-#!/usr/bin/env python3
-
 import collections.abc
 import errno
 import socket
diff --git a/Lib/timeit.py b/Lib/timeit.py
old mode 100644
new mode 100755
diff --git a/Lib/token.py b/Lib/token.py
old mode 100755
new mode 100644
diff --git a/Lib/trace.py b/Lib/trace.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/bytedesign.py b/Lib/turtledemo/bytedesign.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/clock.py b/Lib/turtledemo/clock.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/forest.py b/Lib/turtledemo/forest.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/fractalcurves.py b/Lib/turtledemo/fractalcurves.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/lindenmayer.py b/Lib/turtledemo/lindenmayer.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/minimal_hanoi.py b/Lib/turtledemo/minimal_hanoi.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/paint.py b/Lib/turtledemo/paint.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/peace.py b/Lib/turtledemo/peace.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/penrose.py b/Lib/turtledemo/penrose.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/planet_and_moon.py b/Lib/turtledemo/planet_and_moon.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/tree.py b/Lib/turtledemo/tree.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/two_canvases.py b/Lib/turtledemo/two_canvases.py
old mode 100644
new mode 100755
diff --git a/Lib/turtledemo/yinyang.py b/Lib/turtledemo/yinyang.py
old mode 100644
new mode 100755
diff --git a/Lib/webbrowser.py b/Lib/webbrowser.py
old mode 100644
new mode 100755
diff --git a/Mac/Tools/bundlebuilder.py b/Mac/Tools/bundlebuilder.py
old mode 100644
new mode 100755
diff --git a/Misc/NEWS b/Misc/NEWS
index ed9eafbfb65..a5e8482b473 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -334,6 +334,12 @@ Build
 Tools/Demos
 -----------
 
+- Issue #19936: Added executable bits or shebang lines to Python scripts which
+  requires them.  Disable executable bits and shebang lines in test and
+  benchmark files in order to prevent using a random system python, and in
+  source files of modules which don't provide command line interface.  Fixed
+  shebang line to use python3 executable in the unittestgui script.
+
 - Issue #18960: 2to3 and the findnocoding.py script now ignore the source
   encoding declaration on the second line if the first line contains anything
   except a comment.
diff --git a/Modules/_ctypes/libffi/generate-ios-source-and-headers.py b/Modules/_ctypes/libffi/generate-ios-source-and-headers.py
old mode 100644
new mode 100755
diff --git a/Modules/_ctypes/libffi/generate-osx-source-and-headers.py b/Modules/_ctypes/libffi/generate-osx-source-and-headers.py
old mode 100644
new mode 100755
diff --git a/Modules/_decimal/tests/bench.py b/Modules/_decimal/tests/bench.py
old mode 100644
new mode 100755
diff --git a/Modules/_decimal/tests/deccheck.py b/Modules/_decimal/tests/deccheck.py
old mode 100644
new mode 100755
diff --git a/Objects/typeslots.py b/Objects/typeslots.py
old mode 100644
new mode 100755
diff --git a/Tools/gdb/libpython.py b/Tools/gdb/libpython.py
old mode 100644
new mode 100755
diff --git a/Tools/i18n/makelocalealias.py b/Tools/i18n/makelocalealias.py
old mode 100644
new mode 100755
diff --git a/Tools/pybench/Setup.py b/Tools/pybench/Setup.py
old mode 100644
new mode 100755
diff --git a/Tools/pybench/clockres.py b/Tools/pybench/clockres.py
old mode 100644
new mode 100755
diff --git a/Tools/pybench/systimes.py b/Tools/pybench/systimes.py
old mode 100644
new mode 100755
diff --git a/Tools/scripts/run_tests.py b/Tools/scripts/run_tests.py
old mode 100755
new mode 100644
diff --git a/Tools/ssl/make_ssl_data.py b/Tools/ssl/make_ssl_data.py
old mode 100644
new mode 100755
diff --git a/Tools/stringbench/stringbench.py b/Tools/stringbench/stringbench.py
old mode 100755
new mode 100644
diff --git a/Tools/unicode/comparecodecs.py b/Tools/unicode/comparecodecs.py
old mode 100644
new mode 100755
diff --git a/Tools/unittestgui/unittestgui.py b/Tools/unittestgui/unittestgui.py
old mode 100644
new mode 100755
index 09a20e28e78..c3b5fa45842
--- a/Tools/unittestgui/unittestgui.py
+++ b/Tools/unittestgui/unittestgui.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 """
 GUI framework and application for use with Python unit testing framework.
 Execute tests written using the framework provided by the 'unittest' module.