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The equivalent of used "tr" command is .upper(), not .swapcase().
Instead of the loop
 for s in sys.stdin.read(): sys.stdout.write(s.upper())
you can write just
 sys.stdout.write(sys.stdin.read().upper())
But actually the loop is needed for testing purpose.
 while True:
 b = sys.stdin.buffer.read(1)
 if not b:
 break
 sys.stdout.buffer.write(b.upper())
And sys.executable should be escaped for the case of spaces or other special symbols in the path.
All this complicates tests too much. I prefer to skip some tests on Android.