10. 完整的语法规范

这是完整的Python语法，它被送入解析器生成器，以生成解析Python源文件的解析器：

  1. # Grammar for Python
  2.  
  3. # NOTE WELL: You should also follow all the steps listed at
  4. # https://devguide.python.org/grammar/
  5.  
  6. # Start symbols for the grammar:
  7. #       single_input is a single interactive statement;
  8. #       file_input is a module or sequence of commands read from an input file;
  9. #       eval_input is the input for the eval() functions.
  10. #       func_type_input is a PEP 484 Python 2 function type comment
  11. # NB: compound_stmt in single_input is followed by extra NEWLINE!
  12. # NB: due to the way TYPE_COMMENT is tokenized it will always be followed by a NEWLINE
  13. single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE
  14. file_input: (NEWLINE | stmt)* ENDMARKER
  15. eval_input: testlist NEWLINE* ENDMARKER
  16.  
  17. decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE
  18. decorators: decorator+
  19. decorated: decorators (classdef | funcdef | async_funcdef)
  20.  
  21. async_funcdef: ASYNC funcdef
  22. funcdef: 'def' NAME parameters ['->' test] ':' [TYPE_COMMENT] func_body_suite
  23.  
  24. parameters: '(' [typedargslist] ')'
  25.  
  26. # The following definition for typedarglist is equivalent to this set of rules:
  27. #
  28. #     arguments = argument (',' [TYPE_COMMENT] argument)*
  29. #     argument = tfpdef ['=' test]
  30. #     kwargs = '**' tfpdef [','] [TYPE_COMMENT]
  31. #     args = '*' [tfpdef]
  32. #     kwonly_kwargs = (',' [TYPE_COMMENT] argument)* (TYPE_COMMENT | [',' [TYPE_COMMENT] [kwargs]])
  33. #     args_kwonly_kwargs = args kwonly_kwargs | kwargs
  34. #     poskeyword_args_kwonly_kwargs = arguments ( TYPE_COMMENT | [',' [TYPE_COMMENT] [args_kwonly_kwargs]])
  35. #     typedargslist_no_posonly  = poskeyword_args_kwonly_kwargs | args_kwonly_kwargs
  36. #     typedarglist = (arguments ',' [TYPE_COMMENT] '/' [',' [[TYPE_COMMENT] typedargslist_no_posonly]])|(typedargslist_no_posonly)"
  37. #
  38. # It needs to be fully expanded to allow our LL(1) parser to work on it.
  39.  
  40. typedargslist: (
  41.   (tfpdef ['=' test] (',' [TYPE_COMMENT] tfpdef ['=' test])* ',' [TYPE_COMMENT] '/' [',' [ [TYPE_COMMENT] tfpdef ['=' test] (
  42.         ',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] [
  43.         '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]])
  44.       | '**' tfpdef [','] [TYPE_COMMENT]]])
  45.   | '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]])
  46.   | '**' tfpdef [','] [TYPE_COMMENT]]] )
  47. |  (tfpdef ['=' test] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] [
  48.    '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]])
  49.   | '**' tfpdef [','] [TYPE_COMMENT]]])
  50.   | '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]])
  51.   | '**' tfpdef [','] [TYPE_COMMENT])
  52. )
  53. tfpdef: NAME [':' test]
  54.  
  55. # The following definition for varargslist is equivalent to this set of rules:
  56. #
  57. #     arguments = argument (',' argument )*
  58. #     argument = vfpdef ['=' test]
  59. #     kwargs = '**' vfpdef [',']
  60. #     args = '*' [vfpdef]
  61. #     kwonly_kwargs = (',' argument )* [',' [kwargs]]
  62. #     args_kwonly_kwargs = args kwonly_kwargs | kwargs
  63. #     poskeyword_args_kwonly_kwargs = arguments [',' [args_kwonly_kwargs]]
  64. #     vararglist_no_posonly = poskeyword_args_kwonly_kwargs | args_kwonly_kwargs
  65. #     varargslist = arguments ',' '/' [','[(vararglist_no_posonly)]] | (vararglist_no_posonly)
  66. #
  67. # It needs to be fully expanded to allow our LL(1) parser to work on it.
  68.  
  69. varargslist: vfpdef ['=' test ](',' vfpdef ['=' test])* ',' '/' [',' [ (vfpdef ['=' test] (',' vfpdef ['=' test])* [',' [
  70.         '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
  71.       | '**' vfpdef [',']]]
  72.   | '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
  73.   | '**' vfpdef [',']) ]] | (vfpdef ['=' test] (',' vfpdef ['=' test])* [',' [
  74.         '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
  75.       | '**' vfpdef [',']]]
  76.   | '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]]
  77.   | '**' vfpdef [',']
  78. )
  79. vfpdef: NAME
  80.  
  81. stmt: simple_stmt | compound_stmt
  82. simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE
  83. small_stmt: (expr_stmt | del_stmt | pass_stmt | flow_stmt |
  84.              import_stmt | global_stmt | nonlocal_stmt | assert_stmt)
  85. expr_stmt: testlist_star_expr (annassign | augassign (yield_expr|testlist) |
  86.                      [('=' (yield_expr|testlist_star_expr))+ [TYPE_COMMENT]] )
  87. annassign: ':' test ['=' (yield_expr|testlist_star_expr)]
  88. testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']
  89. augassign: ('+=' | '-=' | '*=' | '@=' | '/=' | '%=' | '&=' | '|=' | '^=' |
  90.             '<<=' | '>>=' | '**=' | '//=')
  91. # For normal and annotated assignments, additional restrictions enforced by the interpreter
  92. del_stmt: 'del' exprlist
  93. pass_stmt: 'pass'
  94. flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt
  95. break_stmt: 'break'
  96. continue_stmt: 'continue'
  97. return_stmt: 'return' [testlist_star_expr]
  98. yield_stmt: yield_expr
  99. raise_stmt: 'raise' [test ['from' test]]
  100. import_stmt: import_name | import_from
  101. import_name: 'import' dotted_as_names
  102. # note below: the ('.' | '...') is necessary because '...' is tokenized as ELLIPSIS
  103. import_from: ('from' (('.' | '...')* dotted_name | ('.' | '...')+)
  104.               'import' ('*' | '(' import_as_names ')' | import_as_names))
  105. import_as_name: NAME ['as' NAME]
  106. dotted_as_name: dotted_name ['as' NAME]
  107. import_as_names: import_as_name (',' import_as_name)* [',']
  108. dotted_as_names: dotted_as_name (',' dotted_as_name)*
  109. dotted_name: NAME ('.' NAME)*
  110. global_stmt: 'global' NAME (',' NAME)*
  111. nonlocal_stmt: 'nonlocal' NAME (',' NAME)*
  112. assert_stmt: 'assert' test [',' test]
  113.  
  114. compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated | async_stmt
  115. async_stmt: ASYNC (funcdef | with_stmt | for_stmt)
  116. if_stmt: 'if' namedexpr_test ':' suite ('elif' namedexpr_test ':' suite)* ['else' ':' suite]
  117. while_stmt: 'while' namedexpr_test ':' suite ['else' ':' suite]
  118. for_stmt: 'for' exprlist 'in' testlist ':' [TYPE_COMMENT] suite ['else' ':' suite]
  119. try_stmt: ('try' ':' suite
  120.            ((except_clause ':' suite)+
  121.             ['else' ':' suite]
  122.             ['finally' ':' suite] |
  123.            'finally' ':' suite))
  124. with_stmt: 'with' with_item (',' with_item)*  ':' [TYPE_COMMENT] suite
  125. with_item: test ['as' expr]
  126. # NB compile.c makes sure that the default except clause is last
  127. except_clause: 'except' [test ['as' NAME]]
  128. suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT
  129.  
  130. namedexpr_test: test [':=' test]
  131. test: or_test ['if' or_test 'else' test] | lambdef
  132. test_nocond: or_test | lambdef_nocond
  133. lambdef: 'lambda' [varargslist] ':' test
  134. lambdef_nocond: 'lambda' [varargslist] ':' test_nocond
  135. or_test: and_test ('or' and_test)*
  136. and_test: not_test ('and' not_test)*
  137. not_test: 'not' not_test | comparison
  138. comparison: expr (comp_op expr)*
  139. # <> isn't actually a valid comparison operator in Python. It's here for the
  140. # sake of a __future__ import described in PEP 401 (which really works :-)
  141. comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not'
  142. star_expr: '*' expr
  143. expr: xor_expr ('|' xor_expr)*
  144. xor_expr: and_expr ('^' and_expr)*
  145. and_expr: shift_expr ('&' shift_expr)*
  146. shift_expr: arith_expr (('<<'|'>>') arith_expr)*
  147. arith_expr: term (('+'|'-') term)*
  148. term: factor (('*'|'@'|'/'|'%'|'//') factor)*
  149. factor: ('+'|'-'|'~') factor | power
  150. power: atom_expr ['**' factor]
  151. atom_expr: [AWAIT] atom trailer*
  152. atom: ('(' [yield_expr|testlist_comp] ')' |
  153.        '[' [testlist_comp] ']' |
  154.        '{' [dictorsetmaker] '}' |
  155.        NAME | NUMBER | STRING+ | '...' | 'None' | 'True' | 'False')
  156. testlist_comp: (namedexpr_test|star_expr) ( comp_for | (',' (namedexpr_test|star_expr))* [','] )
  157. trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME
  158. subscriptlist: subscript (',' subscript)* [',']
  159. subscript: test | [test] ':' [test] [sliceop]
  160. sliceop: ':' [test]
  161. exprlist: (expr|star_expr) (',' (expr|star_expr))* [',']
  162. testlist: test (',' test)* [',']
  163. dictorsetmaker: ( ((test ':' test | '**' expr)
  164.                    (comp_for | (',' (test ':' test | '**' expr))* [','])) |
  165.                   ((test | star_expr)
  166.                    (comp_for | (',' (test | star_expr))* [','])) )
  167.  
  168. classdef: 'class' NAME ['(' [arglist] ')'] ':' suite
  169.  
  170. arglist: argument (',' argument)*  [',']
  171.  
  172. # The reason that keywords are test nodes instead of NAME is that using NAME
  173. # results in an ambiguity. ast.c makes sure it's a NAME.
  174. # "test '=' test" is really "keyword '=' test", but we have no such token.
  175. # These need to be in a single rule to avoid grammar that is ambiguous
  176. # to our LL(1) parser. Even though 'test' includes '*expr' in star_expr,
  177. # we explicitly match '*' here, too, to give it proper precedence.
  178. # Illegal combinations and orderings are blocked in ast.c:
  179. # multiple (test comp_for) arguments are blocked; keyword unpackings
  180. # that precede iterable unpackings are blocked; etc.
  181. argument: ( test [comp_for] |
  182.             test ':=' test |
  183.             test '=' test |
  184.             '**' test |
  185.             '*' test )
  186.  
  187. comp_iter: comp_for | comp_if
  188. sync_comp_for: 'for' exprlist 'in' or_test [comp_iter]
  189. comp_for: [ASYNC] sync_comp_for
  190. comp_if: 'if' test_nocond [comp_iter]
  191.  
  192. # not used in grammar, but may appear in "node" passed from Parser to Compiler
  193. encoding_decl: NAME
  194.  
  195. yield_expr: 'yield' [yield_arg]
  196. yield_arg: 'from' test | testlist_star_expr
  197.  
  198. # the TYPE_COMMENT in suites is only parsed for funcdefs,
  199. # but can't go elsewhere due to ambiguity
  200. func_body_suite: simple_stmt | NEWLINE [TYPE_COMMENT NEWLINE] INDENT stmt+ DEDENT
  201.  
  202. func_type_input: func_type NEWLINE* ENDMARKER
  203. func_type: '(' [typelist] ')' '->' test
  204. # typelist is a modified typedargslist (see above)
  205. typelist: (test (',' test)* [','
  206.        ['*' [test] (',' test)* [',' '**' test] | '**' test]]
  207.      |  '*' [test] (',' test)* [',' '**' test] | '**' test)