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# Grammar for Python # NOTE WELL: You should also follow all the steps listed at # https://devguide.python.org/grammar/ # Start symbols for the grammar: # single_input is a single interactive statement; # file_input is a module or sequence of commands read from an input file; # eval_input is the input for the eval() functions. # func_type_input is a PEP 484 Python 2 function type comment # NB: compound_stmt in single_input is followed by extra NEWLINE! # NB: due to the way TYPE_COMMENT is tokenized it will always be followed by a NEWLINE single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE file_input: (NEWLINE | stmt)* ENDMARKER eval_input: testlist NEWLINE* ENDMARKER decorator: '@' namedexpr_test NEWLINE decorators: decorator+ decorated: decorators (classdef | funcdef | async_funcdef) async_funcdef: ASYNC funcdef funcdef: 'def' NAME parameters ['->' test] ':' [TYPE_COMMENT] func_body_suite parameters: '(' [typedargslist] ')' # The following definition for typedarglist is equivalent to this set of rules: # # arguments = argument (',' [TYPE_COMMENT] argument)* # argument = tfpdef ['=' test] # kwargs = '**' tfpdef [','] [TYPE_COMMENT] # args = '*' [tfpdef] # kwonly_kwargs = (',' [TYPE_COMMENT] argument)* (TYPE_COMMENT | [',' [TYPE_COMMENT] [kwargs]]) # args_kwonly_kwargs = args kwonly_kwargs | kwargs # poskeyword_args_kwonly_kwargs = arguments ( TYPE_COMMENT | [',' [TYPE_COMMENT] [args_kwonly_kwargs]]) # typedargslist_no_posonly = poskeyword_args_kwonly_kwargs | args_kwonly_kwargs # typedarglist = (arguments ',' [TYPE_COMMENT] '/' [',' [[TYPE_COMMENT] typedargslist_no_posonly]])|(typedargslist_no_posonly)" # # It needs to be fully expanded to allow our LL(1) parser to work on it. typedargslist: ( (tfpdef ['=' test] (',' [TYPE_COMMENT] tfpdef ['=' test])* ',' [TYPE_COMMENT] '/' [',' [ [TYPE_COMMENT] tfpdef ['=' test] ( ',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] [ '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]]) | '**' tfpdef [','] [TYPE_COMMENT]]]) | '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]]) | '**' tfpdef [','] [TYPE_COMMENT]]] ) | (tfpdef ['=' test] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] [ '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]]) | '**' tfpdef [','] [TYPE_COMMENT]]]) | '*' [tfpdef] (',' [TYPE_COMMENT] tfpdef ['=' test])* (TYPE_COMMENT | [',' [TYPE_COMMENT] ['**' tfpdef [','] [TYPE_COMMENT]]]) | '**' tfpdef [','] [TYPE_COMMENT]) ) tfpdef: NAME [':' test] # The following definition for varargslist is equivalent to this set of rules: # # arguments = argument (',' argument )* # argument = vfpdef ['=' test] # kwargs = '**' vfpdef [','] # args = '*' [vfpdef] # kwonly_kwargs = (',' argument )* [',' [kwargs]] # args_kwonly_kwargs = args kwonly_kwargs | kwargs # poskeyword_args_kwonly_kwargs = arguments [',' [args_kwonly_kwargs]] # vararglist_no_posonly = poskeyword_args_kwonly_kwargs | args_kwonly_kwargs # varargslist = arguments ',' '/' [','[(vararglist_no_posonly)]] | (vararglist_no_posonly) # # It needs to be fully expanded to allow our LL(1) parser to work on it. varargslist: vfpdef ['=' test ](',' vfpdef ['=' test])* ',' '/' [',' [ (vfpdef ['=' test] (',' vfpdef ['=' test])* [',' [ '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]] | '**' vfpdef [',']]] | '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]] | '**' vfpdef [',']) ]] | (vfpdef ['=' test] (',' vfpdef ['=' test])* [',' [ '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]] | '**' vfpdef [',']]] | '*' [vfpdef] (',' vfpdef ['=' test])* [',' ['**' vfpdef [',']]] | '**' vfpdef [','] ) vfpdef: NAME stmt: simple_stmt | compound_stmt simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE small_stmt: (expr_stmt | del_stmt | pass_stmt | flow_stmt | import_stmt | global_stmt | nonlocal_stmt | assert_stmt) expr_stmt: testlist_star_expr (annassign | augassign (yield_expr|testlist) | [('=' (yield_expr|testlist_star_expr))+ [TYPE_COMMENT]] ) annassign: ':' test ['=' (yield_expr|testlist_star_expr)] testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [','] augassign: ('+=' | '-=' | '*=' | '@=' | '/=' | '%=' | '&=' | '|=' | '^=' | '<<=' | '>>=' | '**=' | '//=') # For normal and annotated assignments, additional restrictions enforced by the interpreter del_stmt: 'del' exprlist pass_stmt: 'pass' flow_stmt: break_stmt | continue_stmt | return_stmt | raise_stmt | yield_stmt break_stmt: 'break' continue_stmt: 'continue' return_stmt: 'return' [testlist_star_expr] yield_stmt: yield_expr raise_stmt: 'raise' [test ['from' test]] import_stmt: import_name | import_from import_name: 'import' dotted_as_names # note below: the ('.' | '...') is necessary because '...' is tokenized as ELLIPSIS import_from: ('from' (('.' | '...')* dotted_name | ('.' | '...')+) 'import' ('*' | '(' import_as_names ')' | import_as_names)) import_as_name: NAME ['as' NAME] dotted_as_name: dotted_name ['as' NAME] import_as_names: import_as_name (',' import_as_name)* [','] dotted_as_names: dotted_as_name (',' dotted_as_name)* dotted_name: NAME ('.' NAME)* global_stmt: 'global' NAME (',' NAME)* nonlocal_stmt: 'nonlocal' NAME (',' NAME)* assert_stmt: 'assert' test [',' test] compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated | async_stmt async_stmt: ASYNC (funcdef | with_stmt | for_stmt) if_stmt: 'if' namedexpr_test ':' suite ('elif' namedexpr_test ':' suite)* ['else' ':' suite] while_stmt: 'while' namedexpr_test ':' suite ['else' ':' suite] for_stmt: 'for' exprlist 'in' testlist ':' [TYPE_COMMENT] suite ['else' ':' suite] try_stmt: ('try' ':' suite ((except_clause ':' suite)+ ['else' ':' suite] ['finally' ':' suite] | 'finally' ':' suite)) with_stmt: 'with' with_item (',' with_item)* ':' [TYPE_COMMENT] suite with_item: test ['as' expr] # NB compile.c makes sure that the default except clause is last except_clause: 'except' [test ['as' NAME]] suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT namedexpr_test: test [':=' test] test: or_test ['if' or_test 'else' test] | lambdef test_nocond: or_test | lambdef_nocond lambdef: 'lambda' [varargslist] ':' test lambdef_nocond: 'lambda' [varargslist] ':' test_nocond or_test: and_test ('or' and_test)* and_test: not_test ('and' not_test)* not_test: 'not' not_test | comparison comparison: expr (comp_op expr)* # <> isn't actually a valid comparison operator in Python. It's here for the # sake of a __future__ import described in PEP 401 (which really works :-) comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not' star_expr: '*' expr expr: xor_expr ('|' xor_expr)* xor_expr: and_expr ('^' and_expr)* and_expr: shift_expr ('&' shift_expr)* shift_expr: arith_expr (('<<'|'>>') arith_expr)* arith_expr: term (('+'|'-') term)* term: factor (('*'|'@'|'/'|'%'|'//') factor)* factor: ('+'|'-'|'~') factor | power power: atom_expr ['**' factor] atom_expr: [AWAIT] atom trailer* atom: ('(' [yield_expr|testlist_comp] ')' | '[' [testlist_comp] ']' | '{' [dictorsetmaker] '}' | NAME | NUMBER | STRING+ | '...' | 'None' | 'True' | 'False') testlist_comp: (namedexpr_test|star_expr) ( comp_for | (',' (namedexpr_test|star_expr))* [','] ) trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME subscriptlist: subscript (',' subscript)* [','] subscript: test | [test] ':' [test] [sliceop] sliceop: ':' [test] exprlist: (expr|star_expr) (',' (expr|star_expr))* [','] testlist: test (',' test)* [','] dictorsetmaker: ( ((test ':' test | '**' expr) (comp_for | (',' (test ':' test | '**' expr))* [','])) | ((test | star_expr) (comp_for | (',' (test | star_expr))* [','])) ) classdef: 'class' NAME ['(' [arglist] ')'] ':' suite arglist: argument (',' argument)* [','] # The reason that keywords are test nodes instead of NAME is that using NAME # results in an ambiguity. ast.c makes sure it's a NAME. # "test '=' test" is really "keyword '=' test", but we have no such token. # These need to be in a single rule to avoid grammar that is ambiguous # to our LL(1) parser. Even though 'test' includes '*expr' in star_expr, # we explicitly match '*' here, too, to give it proper precedence. # Illegal combinations and orderings are blocked in ast.c: # multiple (test comp_for) arguments are blocked; keyword unpackings # that precede iterable unpackings are blocked; etc. argument: ( test [comp_for] | test ':=' test | test '=' test | '**' test | '*' test ) comp_iter: comp_for | comp_if sync_comp_for: 'for' exprlist 'in' or_test [comp_iter] comp_for: [ASYNC] sync_comp_for comp_if: 'if' test_nocond [comp_iter] # not used in grammar, but may appear in "node" passed from Parser to Compiler encoding_decl: NAME yield_expr: 'yield' [yield_arg] yield_arg: 'from' test | testlist_star_expr # the TYPE_COMMENT in suites is only parsed for funcdefs, # but can't go elsewhere due to ambiguity func_body_suite: simple_stmt | NEWLINE [TYPE_COMMENT NEWLINE] INDENT stmt+ DEDENT func_type_input: func_type NEWLINE* ENDMARKER func_type: '(' [typelist] ')' '->' test # typelist is a modified typedargslist (see above) typelist: (test (',' test)* [',' ['*' [test] (',' test)* [',' '**' test] | '**' test]] | '*' [test] (',' test)* [',' '**' test] | '**' test)