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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"

"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">

<head>

<title>10. Full Grammar specification — Python 3.3.7 documentation</title>

var DOCUMENTATION_OPTIONS = {

URL_ROOT: '../',

VERSION: '3.3.7',

COLLAPSE_INDEX: false,

FILE_SUFFIX: '.html',

HAS_SOURCE: true

};

</script>

title="Search within Python 3.3.7 documentation"

href="../_static/opensearch.xml"/>

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<h1>10. Full Grammar specification<a class="headerlink" href="#full-grammar-specification" title="Permalink to this headline">¶</a></h1>

This is the full Python grammar, as it is read by the parser generator and used

to parse Python source files:

<div class="highlight-python3"><div class="highlight"><pre># 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 <[email protected]> will probably be listening there.

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

# "How to Change Python's 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.

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

single_input: NEWLINE | simple_stmt | compound_stmt NEWLINE

file_input: (NEWLINE | stmt)* ENDMARKER

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

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

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

tfpdef: NAME [':' test]

varargslist: (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 (augassign (yield_expr|testlist) |

('=' (yield_expr|testlist_star_expr))*)

testlist_star_expr: (test|star_expr) (',' (test|star_expr))* [',']

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

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

# For normal 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]

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]

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' with_item (',' with_item)* ':' 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

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

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 trailer* ['**' factor]

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

'[' [testlist_comp] ']' |

'{' [dictorsetmaker] '}' |

testlist_comp: (test|star_expr) ( comp_for | (',' (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 (comp_for | (',' test ':' test)* [','])) |

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

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

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

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

|'**' test)

# 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.

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

comp_iter: comp_for | comp_if

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

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

</pre></div>

</div>

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