# Grammar for Python

# Note:  Changing the grammar specified in this file will most likely

#        require corresponding changes in the parser module

#        (../Modules/parsermodule.c).  If you can't make the changes to

#        that module yourself, please co-ordinate the required changes

#        with someone who can; ask around on python-dev for help.  Fred

#        Drake <fdrake@acm.org> will probably be listening there.

# NOTE WELL: You should also follow all the steps listed in PEP 306,

# "How to Change Python's Grammar"

# Commands for Kees Blom's railroad program

#diagram:token NAME

#diagram:token NUMBER

#diagram:token STRING

#diagram:token NEWLINE

#diagram:token ENDMARKER

#diagram:token INDENT

#diagram:output\input python.bla

#diagram:token DEDENT

#diagram:output\textwidth 20.04cm\oddsidemargin  0.0cm\evensidemargin 0.0cm

#diagram:rules

# Start symbols for the grammar:

#	file_input is a module or sequence of commands read from an input file;

#	single_input is a single interactive statement;

#	eval_input is the input for the eval() and input() functions.

# NB: compound_stmt in single_input is followed by extra NEWLINE!

file_input: (NEWLINE | stmt)* ENDMARKER

single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE

eval_input: testlist NEWLINE* ENDMARKER

decorator: '@' dotted_name [ '(' [arglist] ')' ] NEWLINE

decorators: decorator+

decorated: decorators (classdef | funcdef)

funcdef: 'def' NAME parameters ['->' test] ':' suite

parameters: '(' [typedargslist] ')'

typedargslist: ((tfpdef ['=' test] ',')*

                ('*' [tname] (',' tname ['=' test])* [',' '**' tname] | '**' tname)

                | tfpdef ['=' test] (',' tfpdef ['=' test])* [','])

tname: NAME [':' test]

tfpdef: tname | '(' tfplist ')'

tfplist: tfpdef (',' tfpdef)* [',']

varargslist: ((vfpdef ['=' test] ',')*

              ('*' [vname] (',' vname ['=' test])*  [',' '**' vname] | '**' vname)

              | vfpdef ['=' test] (',' vfpdef ['=' test])* [','])

vname: NAME

vfpdef: vname | '(' vfplist ')'

vfplist: vfpdef (',' vfpdef)* [',']

stmt: simple_stmt | compound_stmt

simple_stmt: small_stmt (';' small_stmt)* [';'] NEWLINE

small_stmt: (expr_stmt | print_stmt  | del_stmt | pass_stmt | flow_stmt |

             import_stmt | global_stmt | exec_stmt | assert_stmt)

expr_stmt: testlist (augassign (yield_expr|testlist) |

                     ('=' (yield_expr|testlist))*)

augassign: ('+=' | '-=' | '*=' | '/=' | '%=' | '&=' | '|=' | '^=' |

            '<<=' | '>>=' | '**=' | '//=')

# For normal assignments, additional restrictions enforced by the interpreter

print_stmt: 'print' ( [ test (',' test)* [','] ] |

                      '>>' test [ (',' test)+ [','] ] )

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]

yield_stmt: yield_expr

raise_stmt: 'raise' [test ['from' test | ',' test [',' test]]]

import_stmt: import_name | import_from

import_name: 'import' dotted_as_names

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' | 'nonlocal') NAME (',' NAME)*

exec_stmt: 'exec' expr ['in' test [',' test]]

assert_stmt: 'assert' test [',' test]

compound_stmt: if_stmt | while_stmt | for_stmt | try_stmt | with_stmt | funcdef | classdef | decorated

if_stmt: 'if' test ':' suite ('elif' test ':' suite)* ['else' ':' suite]

while_stmt: 'while' test ':' suite ['else' ':' suite]

for_stmt: 'for' exprlist 'in' testlist ':' suite ['else' ':' suite]

try_stmt: ('try' ':' suite

           ((except_clause ':' suite)+

	    ['else' ':' suite]

	    ['finally' ':' suite] |

	   'finally' ':' suite))

with_stmt: 'with' test [ with_var ] ':' suite

with_var: 'as' expr

# NB compile.c makes sure that the default except clause is last

except_clause: 'except' [test [(',' | 'as') test]]

suite: simple_stmt | NEWLINE INDENT stmt+ DEDENT

# Backward compatibility cruft to support:

# [ x for x in lambda: True, lambda: False if x() ]

# even while also allowing:

# lambda x: 5 if x else 2

# (But not a mix of the two)

testlist_safe: old_test [(',' old_test)+ [',']]

old_test: or_test | old_lambdef

old_lambdef: 'lambda' [varargslist] ':' old_test

test: or_test ['if' or_test 'else' test] | lambdef

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)*

comp_op: '<'|'>'|'=='|'>='|'<='|'<>'|'!='|'in'|'not' 'in'|'is'|'is' 'not'

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 trailer* ['**' factor]

atom: ('(' [yield_expr|testlist_gexp] ')' |

       '[' [listmaker] ']' |

       '{' [dictsetmaker] '}' |

       '`' testlist1 '`' |

       NAME | NUMBER | STRING+ | '.' '.' '.')

listmaker: test ( comp_for | (',' test)* [','] )

testlist_gexp: test ( comp_for | (',' test)* [','] )

lambdef: 'lambda' [varargslist] ':' test

trailer: '(' [arglist] ')' | '[' subscriptlist ']' | '.' NAME

subscriptlist: subscript (',' subscript)* [',']

subscript: test | [test] ':' [test] [sliceop]

sliceop: ':' [test]

exprlist: expr (',' expr)* [',']

testlist: test (',' test)* [',']

dictsetmaker: ( (test ':' test (comp_for | (',' test ':' test)* [','])) |

                (test (comp_for | (',' test)* [','])) )

classdef: 'class' NAME ['(' [arglist] ')'] ':' suite

arglist: (argument ',')* (argument [',']

                         |'*' test (',' argument)* [',' '**' test] 

                         |'**' test)

argument: test [comp_for] | test '=' test  # Really [keyword '='] test

comp_iter: comp_for | comp_if

comp_for: 'for' exprlist 'in' testlist_safe [comp_iter]

comp_if: 'if' old_test [comp_iter]

testlist1: test (',' test)*

# not used in grammar, but may appear in "node" passed from Parser to Compiler

encoding_decl: NAME

yield_expr: 'yield' [testlist]