Highlight punctuation that does not fall into any syntax group

README.rst

 Options used by the script
 ~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+``python_highlight_default_punctuation``
+  Highlight punctuation that does not fall into any syntax group
 ``python_highlight_builtins``
   Highlight builtin functions and objects
 ``python_highlight_builtin_objs``

syntax.txt

 <
 Options used by the script
 
-  Highlight builtin functions and objects >
+  Highlight punctuation that does not fall into any syntax group >
+    :let python_highlight_default_punctuation
+<  Highlight builtin functions and objects >
     :let python_highlight_builtins = 1
 <  Highlight builtin objects only >
     :let python_highlight_builtin_objs = 1

syntax/python.vim

 " Option names used by the script
 " -------------------------------
 "
+"    python_highlight_default_punctuation   Highlight punctuation that does not
+"                                           fall into any syntax group
 "    python_highlight_builtins              Highlight builtin functions and
 "                                           objects
 "      python_highlight_builtin_objs        Highlight builtin objects only
 call s:EnableByDefault("g:python_slow_sync")
 
 if s:Enabled("g:python_highlight_all")
+  call s:EnableByDefault("g:python_highlight_default_punctuation")
   call s:EnableByDefault("g:python_highlight_builtins")
   if s:Enabled("g:python_highlight_builtins")
     call s:EnableByDefault("g:python_highlight_builtin_objs")
   call s:EnableByDefault("g:python_print_as_function")
 endif
 
+"
+" Default punctuation
+"
+
+if s:Enabled("g:python_highlight_default_punctuation")
+  syn match pythonPunctuation "[^A-Za-z0-9_]"
+endif
+
 "
 " Keywords
 "
     command -nargs=+ HiLink hi def link <args>
   endif
 
+  HiLink pythonPunctuation      Special
+
   HiLink pythonStatement        Statement
   HiLink pythonImport           Include
   HiLink pythonFunction         Function