Add support for Python 3.6 f-string literal and underscore in numbers.

syntax/python.vim

   syn match   pythonStatement   "\<async\s\+for\>" display
 endif
 
+syn cluster pythonExpression contains=pythonStatement,pythonRepeat,pythonConditional,pythonOperator,pythonNumber,pythonHexNumber,pythonOctNumber,pythonBinNumber,pythonFloat,pythonString,pythonBytes,pythonBoolean,pythonBuiltinObj,pythonBuiltinFunc
+
 "
 " Decorators (new in Python 2.4)
 "
   syn region pythonString   start=+"+ skip=+\\\\\|\\"\|\\$+ excludenl end=+"+ end=+$+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,@Spell
   syn region pythonString   start=+"""+ end=+"""+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,pythonDocTest2,pythonSpaceError,@Spell
   syn region pythonString   start=+'''+ end=+'''+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,pythonDocTest,pythonSpaceError,@Spell
+
+  syn region pythonFString   start=+[fF]'+ skip=+\\\\\|\\'\|\\$+ excludenl end=+'+ end=+$+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,@Spell
+  syn region pythonFString   start=+[fF]"+ skip=+\\\\\|\\"\|\\$+ excludenl end=+"+ end=+$+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,@Spell
+  syn region pythonFString   start=+[fF]"""+ end=+"""+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,pythonDocTest2,pythonSpaceError,@Spell
+  syn region pythonFString   start=+[fF]'''+ end=+'''+ keepend contains=pythonBytesEscape,pythonBytesEscapeError,pythonUniEscape,pythonUniEscapeError,pythonDocTest,pythonSpaceError,@Spell
 endif
 
 if s:Python2Syntax()
     syn match pythonStrFormat "{{\|}}" contained containedin=pythonString,pythonUniString,pythonUniRawString,pythonRawString
     syn match pythonStrFormat	"{\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)\=\%(\.\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\[\%(\d\+\|[^!:\}]\+\)\]\)*\%(![rsa]\)\=\%(:\%({\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)}\|\%([^}]\=[<>=^]\)\=[ +-]\=#\=0\=\d*,\=\%(\.\d\+\)\=[bcdeEfFgGnosxX%]\=\)\=\)\=}" contained containedin=pythonString,pythonUniString,pythonUniRawString,pythonRawString
   else
-    syn match pythonStrFormat "{{\|}}" contained containedin=pythonString,pythonRawString
-    syn match pythonStrFormat	"{\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)\=\%(\.\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\[\%(\d\+\|[^!:\}]\+\)\]\)*\%(![rsa]\)\=\%(:\%({\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)}\|\%([^}]\=[<>=^]\)\=[ +-]\=#\=0\=\d*,\=\%(\.\d\+\)\=[bcdeEfFgGnosxX%]\=\)\=\)\=}" contained containedin=pythonString,pythonRawString
+    syn match pythonStrFormat "{{\|}}" contained containedin=pythonString,pythonRawString,pythonFString
+    syn match pythonStrFormat "{\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)\=\%(\.\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\[\%(\d\+\|[^!:\}]\+\)\]\)*\%(![rsa]\)\=\%(:\%({\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)}\|\%([^}]\=[<>=^]\)\=[ +-]\=#\=0\=\d*,\=\%(\.\d\+\)\=[bcdeEfFgGnosxX%]\=\)\=\)\=}" contained containedin=pythonString,pythonRawString
+    syn region pythonStrInterpRegion start="{"he=e+1,rs=e+1 end="\%(![rsa]\)\=\%(:\%({\%(\%([^[:cntrl:][:space:][:punct:][:digit:]]\|_\)\%([^[:cntrl:][:punct:][:space:]]\|_\)*\|\d\+\)}\|\%([^}]\=[<>=^]\)\=[ +-]\=#\=0\=\d*,\=\%(\.\d\+\)\=[bcdeEfFgGnosxX%]\=\)\=\)\=}"hs=s-1,re=s-1 extend contained containedin=pythonFString contains=pythonStrInterpRegion,@pythonExpression
   endif
 endif
 
 
   syn match   pythonOctError	"\<0[oO]\=\o*[8-9]\d*[lL]\=\>" display
   syn match   pythonBinError	"\<0[bB][01]*[2-9]\d*[lL]\=\>" display
+
+  syn match   pythonFloat	"\.\d\+\%([eE][+-]\=\d\+\)\=[jJ]\=\>" display
+  syn match   pythonFloat	"\<\d\+[eE][+-]\=\d\+[jJ]\=\>" display
+  syn match   pythonFloat	"\<\d\+\.\d*\%([eE][+-]\=\d\+\)\=[jJ]\=" display
 else
   syn match   pythonHexError	"\<0[xX]\x*[g-zG-Z]\x*\>" display
   syn match   pythonOctError	"\<0[oO]\=\o*\D\+\d*\>" display
   syn match   pythonBinError	"\<0[bB][01]*\D\+\d*\>" display
 
-  syn match   pythonHexNumber	"\<0[xX]\x\+\>" display
-  syn match   pythonOctNumber "\<0[oO]\o\+\>" display
-  syn match   pythonBinNumber "\<0[bB][01]\+\>" display
+  syn match   pythonHexNumber	"\<0[xX][_0-9a-fA-F]*\x\>" display
+  syn match   pythonOctNumber "\<0[oO][_0-7]*\o\>" display
+  syn match   pythonBinNumber "\<0[bB][_01]*[01]\>" display
 
-  syn match   pythonNumberError	"\<\d\+\D\>" display
-  syn match   pythonNumberError	"\<0\d\+\>" display
+  syn match   pythonNumberError	"\<\d[_0-9]*\D\>" display
+  syn match   pythonNumberError	"\<0[_0-9]\+\>" display
+  syn match   pythonNumberError	"\<\%(_[_0-9]\+\|[_0-9]\+_\)\>" display
   syn match   pythonNumber	"\<\d\>" display
-  syn match   pythonNumber	"\<[1-9]\d\+\>" display
-  syn match   pythonNumber	"\<\d\+[jJ]\>" display
+  syn match   pythonNumber	"\<[1-9][_0-9]*\d\>" display
+  syn match   pythonNumber	"\<\d[jJ]\>" display
+  syn match   pythonNumber	"\<[1-9][_0-9]*\d[jJ]\>" display
 
   syn match   pythonOctError	"\<0[oO]\=\o*[8-9]\d*\>" display
   syn match   pythonBinError	"\<0[bB][01]*[2-9]\d*\>" display
-endif
 
-syn match   pythonFloat		"\.\d\+\%([eE][+-]\=\d\+\)\=[jJ]\=\>" display
-syn match   pythonFloat		"\<\d\+[eE][+-]\=\d\+[jJ]\=\>" display
-syn match   pythonFloat		"\<\d\+\.\d*\%([eE][+-]\=\d\+\)\=[jJ]\=" display
+  syn match   pythonFloat	"\.\d\%([_0-9]*\d\)\=\%([eE][+-]\=\d\%([_0-9]*\d\)\=\)\=[jJ]\=\>" display
+  syn match   pythonFloat	"\<\d\%([_0-9]*\d\)\=[eE][+-]\=\d\%([_0-9]*\d\)\=[jJ]\=\>" display
+  syn match   pythonFloat	"\<\d\%([_0-9]*\d\)\=\.\d\%([_0-9]*\d\)\=\%([eE][+-]\=\d\%([_0-9]*\d\)\=\)\=[jJ]\=" display
+endif
 
 "
 " Builtin objects and types
     HiLink pythonBytesError         Error
     HiLink pythonBytesEscape        Special
     HiLink pythonBytesEscapeError   Error
+    HiLink pythonFString            String
+    HiLink pythonStrInterpRegion    Special
   endif
 
   HiLink pythonStrFormatting    Special

test.py

 
 # Numbers
 
-0 1 2 9 10 0x1f .3 12.34 0j 0j 34.2E-3 0b10 0o77 1023434 0x0
+0 1 2 9 10 0x1f .3 12.34 0j 124j 34.2E-3 0b10 0o77 1023434 0x0
+1_1 1_1.2_2 1_2j 0x_1f 0x1_f 34_56e-3 34_56e+3_1 0o7_7
 
 # Erroneous numbers
 
-077 100L 0xfffffffL 0L 08 0xk 0x  0b102 0o78 0o123LaB
+077 100L 0xfffffffL 0L 08 0xk 0x 0b102 0o78 0o123LaB
+0_ 0_1 _0 0_x1f 0x1f_ 0_b77 0b77_ ._2 .2_ 1_j
 
 # Strings
 
 "${test} ${test ${test}aname $$$ $test+nope"
 b"${test} ${test ${test}aname $$$ $test+nope"
 
+f"{var}...{arr[123]} normal {var['{'] // 0xff} \"xzcb\" 'xzcb' {var['}'] + 1} text"
+f"{expr1 if True or False else expr2} wow {','.join(c.lower() for c in 'asdf')}"
+f"hello {expr:.2f} yes {(lambda: 0b1)():#03x} lol {var!r}"
+
 # Doctests.
 
 """