10. Especificação Completa da Gramática¶
Esta é a gramática completa do Python, derivada diretamente da gramática usada para gerar o analisador sintático de CPython (consulte Grammar/python.gram). A versão aqui omite detalhes relacionados à geração de código e recuperação de erros.
A notação é uma mistura de EBNF e GASE (em inglês, PEG). Em particular, &
seguido por um símbolo, token ou grupo entre parênteses indica um “olhar a frente” positivo (ou seja, é necessário para corresponder, mas não consumido), enquanto !
indica um “olhar a frente” negativo (ou seja, é necessário não combinar). Usamos o separador |
para significar a “escolha ordenada” do GASE (escrito como /
nas gramáticas GASE tradicionais). Veja PEP 617 para mais detalhes sobre a sintaxe da gramática.
# PEG grammar for Python
# ========================= START OF THE GRAMMAR =========================
# General grammatical elements and rules:
#
# * Strings with double quotes (") denote SOFT KEYWORDS
# * Strings with single quotes (') denote KEYWORDS
# * Upper case names (NAME) denote tokens in the Grammar/Tokens file
# * Rule names starting with "invalid_" are used for specialized syntax errors
# - These rules are NOT used in the first pass of the parser.
# - Only if the first pass fails to parse, a second pass including the invalid
# rules will be executed.
# - If the parser fails in the second phase with a generic syntax error, the
# location of the generic failure of the first pass will be used (this avoids
# reporting incorrect locations due to the invalid rules).
# - The order of the alternatives involving invalid rules matter
# (like any rule in PEG).
#
# Grammar Syntax (see PEP 617 for more information):
#
# rule_name: expression
# Optionally, a type can be included right after the rule name, which
# specifies the return type of the C or Python function corresponding to the
# rule:
# rule_name[return_type]: expression
# If the return type is omitted, then a void * is returned in C and an Any in
# Python.
# e1 e2
# Match e1, then match e2.
# e1 | e2
# Match e1 or e2.
# The first alternative can also appear on the line after the rule name for
# formatting purposes. In that case, a | must be used before the first
# alternative, like so:
# rule_name[return_type]:
# | first_alt
# | second_alt
# ( e )
# Match e (allows also to use other operators in the group like '(e)*')
# [ e ] or e?
# Optionally match e.
# e*
# Match zero or more occurrences of e.
# e+
# Match one or more occurrences of e.
# s.e+
# Match one or more occurrences of e, separated by s. The generated parse tree
# does not include the separator. This is otherwise identical to (e (s e)*).
# &e
# Succeed if e can be parsed, without consuming any input.
# !e
# Fail if e can be parsed, without consuming any input.
# ~
# Commit to the current alternative, even if it fails to parse.
#
# STARTING RULES
# ==============
file: [statements] ENDMARKER
interactive: statement_newline
eval: expressions NEWLINE* ENDMARKER
func_type: '(' [type_expressions] ')' '->' expression NEWLINE* ENDMARKER
# GENERAL STATEMENTS
# ==================
statements: statement+
statement: compound_stmt | simple_stmts
statement_newline:
| compound_stmt NEWLINE
| simple_stmts
| NEWLINE
| ENDMARKER
simple_stmts:
| simple_stmt !';' NEWLINE # Not needed, there for speedup
| ';'.simple_stmt+ [';'] NEWLINE
# NOTE: assignment MUST precede expression, else parsing a simple assignment
# will throw a SyntaxError.
simple_stmt:
| assignment
| type_alias
| star_expressions
| return_stmt
| import_stmt
| raise_stmt
| 'pass'
| del_stmt
| yield_stmt
| assert_stmt
| 'break'
| 'continue'
| global_stmt
| nonlocal_stmt
compound_stmt:
| function_def
| if_stmt
| class_def
| with_stmt
| for_stmt
| try_stmt
| while_stmt
| match_stmt
# SIMPLE STATEMENTS
# =================
# NOTE: annotated_rhs may start with 'yield'; yield_expr must start with 'yield'
assignment:
| NAME ':' expression ['=' annotated_rhs ]
| ('(' single_target ')'
| single_subscript_attribute_target) ':' expression ['=' annotated_rhs ]
| (star_targets '=' )+ (yield_expr | star_expressions) !'=' [TYPE_COMMENT]
| single_target augassign ~ (yield_expr | star_expressions)
annotated_rhs: yield_expr | star_expressions
augassign:
| '+='
| '-='
| '*='
| '@='
| '/='
| '%='
| '&='
| '|='
| '^='
| '<<='
| '>>='
| '**='
| '//='
return_stmt:
| 'return' [star_expressions]
raise_stmt:
| 'raise' expression ['from' expression ]
| 'raise'
global_stmt: 'global' ','.NAME+
nonlocal_stmt: 'nonlocal' ','.NAME+
del_stmt:
| 'del' del_targets &(';' | NEWLINE)
yield_stmt: yield_expr
assert_stmt: 'assert' expression [',' expression ]
import_stmt:
| import_name
| import_from
# Import statements
# -----------------
import_name: 'import' dotted_as_names
# note below: the ('.' | '...') is necessary because '...' is tokenized as ELLIPSIS
import_from:
| 'from' ('.' | '...')* dotted_name 'import' import_from_targets
| 'from' ('.' | '...')+ 'import' import_from_targets
import_from_targets:
| '(' import_from_as_names [','] ')'
| import_from_as_names !','
| '*'
import_from_as_names:
| ','.import_from_as_name+
import_from_as_name:
| NAME ['as' NAME ]
dotted_as_names:
| ','.dotted_as_name+
dotted_as_name:
| dotted_name ['as' NAME ]
dotted_name:
| dotted_name '.' NAME
| NAME
# COMPOUND STATEMENTS
# ===================
# Common elements
# ---------------
block:
| NEWLINE INDENT statements DEDENT
| simple_stmts
decorators: ('@' named_expression NEWLINE )+
# Class definitions
# -----------------
class_def:
| decorators class_def_raw
| class_def_raw
class_def_raw:
| 'class' NAME [type_params] ['(' [arguments] ')' ] ':' block
# Function definitions
# --------------------
function_def:
| decorators function_def_raw
| function_def_raw
function_def_raw:
| 'def' NAME [type_params] '(' [params] ')' ['->' expression ] ':' [func_type_comment] block
| ASYNC 'def' NAME [type_params] '(' [params] ')' ['->' expression ] ':' [func_type_comment] block
# Function parameters
# -------------------
params:
| parameters
parameters:
| slash_no_default param_no_default* param_with_default* [star_etc]
| slash_with_default param_with_default* [star_etc]
| param_no_default+ param_with_default* [star_etc]
| param_with_default+ [star_etc]
| star_etc
# Some duplication here because we can't write (',' | &')'),
# which is because we don't support empty alternatives (yet).
slash_no_default:
| param_no_default+ '/' ','
| param_no_default+ '/' &')'
slash_with_default:
| param_no_default* param_with_default+ '/' ','
| param_no_default* param_with_default+ '/' &')'
star_etc:
| '*' param_no_default param_maybe_default* [kwds]
| '*' param_no_default_star_annotation param_maybe_default* [kwds]
| '*' ',' param_maybe_default+ [kwds]
| kwds
kwds:
| '**' param_no_default
# One parameter. This *includes* a following comma and type comment.
#
# There are three styles:
# - No default
# - With default
# - Maybe with default
#
# There are two alternative forms of each, to deal with type comments:
# - Ends in a comma followed by an optional type comment
# - No comma, optional type comment, must be followed by close paren
# The latter form is for a final parameter without trailing comma.
#
param_no_default:
| param ',' TYPE_COMMENT?
| param TYPE_COMMENT? &')'
param_no_default_star_annotation:
| param_star_annotation ',' TYPE_COMMENT?
| param_star_annotation TYPE_COMMENT? &')'
param_with_default:
| param default ',' TYPE_COMMENT?
| param default TYPE_COMMENT? &')'
param_maybe_default:
| param default? ',' TYPE_COMMENT?
| param default? TYPE_COMMENT? &')'
param: NAME annotation?
param_star_annotation: NAME star_annotation
annotation: ':' expression
star_annotation: ':' star_expression
default: '=' expression | invalid_default
# If statement
# ------------
if_stmt:
| 'if' named_expression ':' block elif_stmt
| 'if' named_expression ':' block [else_block]
elif_stmt:
| 'elif' named_expression ':' block elif_stmt
| 'elif' named_expression ':' block [else_block]
else_block:
| 'else' ':' block
# While statement
# ---------------
while_stmt:
| 'while' named_expression ':' block [else_block]
# For statement
# -------------
for_stmt:
| 'for' star_targets 'in' ~ star_expressions ':' [TYPE_COMMENT] block [else_block]
| ASYNC 'for' star_targets 'in' ~ star_expressions ':' [TYPE_COMMENT] block [else_block]
# With statement
# --------------
with_stmt:
| 'with' '(' ','.with_item+ ','? ')' ':' block
| 'with' ','.with_item+ ':' [TYPE_COMMENT] block
| ASYNC 'with' '(' ','.with_item+ ','? ')' ':' block
| ASYNC 'with' ','.with_item+ ':' [TYPE_COMMENT] block
with_item:
| expression 'as' star_target &(',' | ')' | ':')
| expression
# Try statement
# -------------
try_stmt:
| 'try' ':' block finally_block
| 'try' ':' block except_block+ [else_block] [finally_block]
| 'try' ':' block except_star_block+ [else_block] [finally_block]
# Except statement
# ----------------
except_block:
| 'except' expression ['as' NAME ] ':' block
| 'except' ':' block
except_star_block:
| 'except' '*' expression ['as' NAME ] ':' block
finally_block:
| 'finally' ':' block
# Match statement
# ---------------
match_stmt:
| "match" subject_expr ':' NEWLINE INDENT case_block+ DEDENT
subject_expr:
| star_named_expression ',' star_named_expressions?
| named_expression
case_block:
| "case" patterns guard? ':' block
guard: 'if' named_expression
patterns:
| open_sequence_pattern
| pattern
pattern:
| as_pattern
| or_pattern
as_pattern:
| or_pattern 'as' pattern_capture_target
or_pattern:
| '|'.closed_pattern+
closed_pattern:
| literal_pattern
| capture_pattern
| wildcard_pattern
| value_pattern
| group_pattern
| sequence_pattern
| mapping_pattern
| class_pattern
# Literal patterns are used for equality and identity constraints
literal_pattern:
| signed_number !('+' | '-')
| complex_number
| strings
| 'None'
| 'True'
| 'False'
# Literal expressions are used to restrict permitted mapping pattern keys
literal_expr:
| signed_number !('+' | '-')
| complex_number
| strings
| 'None'
| 'True'
| 'False'
complex_number:
| signed_real_number '+' imaginary_number
| signed_real_number '-' imaginary_number
signed_number:
| NUMBER
| '-' NUMBER
signed_real_number:
| real_number
| '-' real_number
real_number:
| NUMBER
imaginary_number:
| NUMBER
capture_pattern:
| pattern_capture_target
pattern_capture_target:
| !"_" NAME !('.' | '(' | '=')
wildcard_pattern:
| "_"
value_pattern:
| attr !('.' | '(' | '=')
attr:
| name_or_attr '.' NAME
name_or_attr:
| attr
| NAME
group_pattern:
| '(' pattern ')'
sequence_pattern:
| '[' maybe_sequence_pattern? ']'
| '(' open_sequence_pattern? ')'
open_sequence_pattern:
| maybe_star_pattern ',' maybe_sequence_pattern?
maybe_sequence_pattern:
| ','.maybe_star_pattern+ ','?
maybe_star_pattern:
| star_pattern
| pattern
star_pattern:
| '*' pattern_capture_target
| '*' wildcard_pattern
mapping_pattern:
| '{' '}'
| '{' double_star_pattern ','? '}'
| '{' items_pattern ',' double_star_pattern ','? '}'
| '{' items_pattern ','? '}'
items_pattern:
| ','.key_value_pattern+
key_value_pattern:
| (literal_expr | attr) ':' pattern
double_star_pattern:
| '**' pattern_capture_target
class_pattern:
| name_or_attr '(' ')'
| name_or_attr '(' positional_patterns ','? ')'
| name_or_attr '(' keyword_patterns ','? ')'
| name_or_attr '(' positional_patterns ',' keyword_patterns ','? ')'
positional_patterns:
| ','.pattern+
keyword_patterns:
| ','.keyword_pattern+
keyword_pattern:
| NAME '=' pattern
# Type statement
# ---------------
type_alias:
| "type" NAME [type_params] '=' expression
# Type parameter declaration
# --------------------------
type_params: '[' type_param_seq ']'
type_param_seq: ','.type_param+ [',']
type_param:
| NAME [type_param_bound]
| '*' NAME
| '**' NAME
type_param_bound: ':' expression
# EXPRESSIONS
# -----------
expressions:
| expression (',' expression )+ [',']
| expression ','
| expression
expression:
| disjunction 'if' disjunction 'else' expression
| disjunction
| lambdef
yield_expr:
| 'yield' 'from' expression
| 'yield' [star_expressions]
star_expressions:
| star_expression (',' star_expression )+ [',']
| star_expression ','
| star_expression
star_expression:
| '*' bitwise_or
| expression
star_named_expressions: ','.star_named_expression+ [',']
star_named_expression:
| '*' bitwise_or
| named_expression
assignment_expression:
| NAME ':=' ~ expression
named_expression:
| assignment_expression
| expression !':='
disjunction:
| conjunction ('or' conjunction )+
| conjunction
conjunction:
| inversion ('and' inversion )+
| inversion
inversion:
| 'not' inversion
| comparison
# Comparison operators
# --------------------
comparison:
| bitwise_or compare_op_bitwise_or_pair+
| bitwise_or
compare_op_bitwise_or_pair:
| eq_bitwise_or
| noteq_bitwise_or
| lte_bitwise_or
| lt_bitwise_or
| gte_bitwise_or
| gt_bitwise_or
| notin_bitwise_or
| in_bitwise_or
| isnot_bitwise_or
| is_bitwise_or
eq_bitwise_or: '==' bitwise_or
noteq_bitwise_or:
| ('!=' ) bitwise_or
lte_bitwise_or: '<=' bitwise_or
lt_bitwise_or: '<' bitwise_or
gte_bitwise_or: '>=' bitwise_or
gt_bitwise_or: '>' bitwise_or
notin_bitwise_or: 'not' 'in' bitwise_or
in_bitwise_or: 'in' bitwise_or
isnot_bitwise_or: 'is' 'not' bitwise_or
is_bitwise_or: 'is' bitwise_or
# Bitwise operators
# -----------------
bitwise_or:
| bitwise_or '|' bitwise_xor
| bitwise_xor
bitwise_xor:
| bitwise_xor '^' bitwise_and
| bitwise_and
bitwise_and:
| bitwise_and '&' shift_expr
| shift_expr
shift_expr:
| shift_expr '<<' sum
| shift_expr '>>' sum
| sum
# Arithmetic operators
# --------------------
sum:
| sum '+' term
| sum '-' term
| term
term:
| term '*' factor
| term '/' factor
| term '//' factor
| term '%' factor
| term '@' factor
| factor
factor:
| '+' factor
| '-' factor
| '~' factor
| power
power:
| await_primary '**' factor
| await_primary
# Primary elements
# ----------------
# Primary elements are things like "obj.something.something", "obj[something]", "obj(something)", "obj" ...
await_primary:
| AWAIT primary
| primary
primary:
| primary '.' NAME
| primary genexp
| primary '(' [arguments] ')'
| primary '[' slices ']'
| atom
slices:
| slice !','
| ','.(slice | starred_expression)+ [',']
slice:
| [expression] ':' [expression] [':' [expression] ]
| named_expression
atom:
| NAME
| 'True'
| 'False'
| 'None'
| strings
| NUMBER
| (tuple | group | genexp)
| (list | listcomp)
| (dict | set | dictcomp | setcomp)
| '...'
group:
| '(' (yield_expr | named_expression) ')'
# Lambda functions
# ----------------
lambdef:
| 'lambda' [lambda_params] ':' expression
lambda_params:
| lambda_parameters
# lambda_parameters etc. duplicates parameters but without annotations
# or type comments, and if there's no comma after a parameter, we expect
# a colon, not a close parenthesis. (For more, see parameters above.)
#
lambda_parameters:
| lambda_slash_no_default lambda_param_no_default* lambda_param_with_default* [lambda_star_etc]
| lambda_slash_with_default lambda_param_with_default* [lambda_star_etc]
| lambda_param_no_default+ lambda_param_with_default* [lambda_star_etc]
| lambda_param_with_default+ [lambda_star_etc]
| lambda_star_etc
lambda_slash_no_default:
| lambda_param_no_default+ '/' ','
| lambda_param_no_default+ '/' &':'
lambda_slash_with_default:
| lambda_param_no_default* lambda_param_with_default+ '/' ','
| lambda_param_no_default* lambda_param_with_default+ '/' &':'
lambda_star_etc:
| '*' lambda_param_no_default lambda_param_maybe_default* [lambda_kwds]
| '*' ',' lambda_param_maybe_default+ [lambda_kwds]
| lambda_kwds
lambda_kwds:
| '**' lambda_param_no_default
lambda_param_no_default:
| lambda_param ','
| lambda_param &':'
lambda_param_with_default:
| lambda_param default ','
| lambda_param default &':'
lambda_param_maybe_default:
| lambda_param default? ','
| lambda_param default? &':'
lambda_param: NAME
# LITERALS
# ========
fstring_middle:
| fstring_replacement_field
| FSTRING_MIDDLE
fstring_replacement_field:
| '{' (yield_expr | star_expressions) '='? [fstring_conversion] [fstring_full_format_spec] '}'
fstring_conversion:
| "!" NAME
fstring_full_format_spec:
| ':' fstring_format_spec*
fstring_format_spec:
| FSTRING_MIDDLE
| fstring_replacement_field
fstring:
| FSTRING_START fstring_middle* FSTRING_END
string: STRING
strings: (fstring|string)+
list:
| '[' [star_named_expressions] ']'
tuple:
| '(' [star_named_expression ',' [star_named_expressions] ] ')'
set: '{' star_named_expressions '}'
# Dicts
# -----
dict:
| '{' [double_starred_kvpairs] '}'
double_starred_kvpairs: ','.double_starred_kvpair+ [',']
double_starred_kvpair:
| '**' bitwise_or
| kvpair
kvpair: expression ':' expression
# Comprehensions & Generators
# ---------------------------
for_if_clauses:
| for_if_clause+
for_if_clause:
| ASYNC 'for' star_targets 'in' ~ disjunction ('if' disjunction )*
| 'for' star_targets 'in' ~ disjunction ('if' disjunction )*
listcomp:
| '[' named_expression for_if_clauses ']'
setcomp:
| '{' named_expression for_if_clauses '}'
genexp:
| '(' ( assignment_expression | expression !':=') for_if_clauses ')'
dictcomp:
| '{' kvpair for_if_clauses '}'
# FUNCTION CALL ARGUMENTS
# =======================
arguments:
| args [','] &')'
args:
| ','.(starred_expression | ( assignment_expression | expression !':=') !'=')+ [',' kwargs ]
| kwargs
kwargs:
| ','.kwarg_or_starred+ ',' ','.kwarg_or_double_starred+
| ','.kwarg_or_starred+
| ','.kwarg_or_double_starred+
starred_expression:
| '*' expression
kwarg_or_starred:
| NAME '=' expression
| starred_expression
kwarg_or_double_starred:
| NAME '=' expression
| '**' expression
# ASSIGNMENT TARGETS
# ==================
# Generic targets
# ---------------
# NOTE: star_targets may contain *bitwise_or, targets may not.
star_targets:
| star_target !','
| star_target (',' star_target )* [',']
star_targets_list_seq: ','.star_target+ [',']
star_targets_tuple_seq:
| star_target (',' star_target )+ [',']
| star_target ','
star_target:
| '*' (!'*' star_target)
| target_with_star_atom
target_with_star_atom:
| t_primary '.' NAME !t_lookahead
| t_primary '[' slices ']' !t_lookahead
| star_atom
star_atom:
| NAME
| '(' target_with_star_atom ')'
| '(' [star_targets_tuple_seq] ')'
| '[' [star_targets_list_seq] ']'
single_target:
| single_subscript_attribute_target
| NAME
| '(' single_target ')'
single_subscript_attribute_target:
| t_primary '.' NAME !t_lookahead
| t_primary '[' slices ']' !t_lookahead
t_primary:
| t_primary '.' NAME &t_lookahead
| t_primary '[' slices ']' &t_lookahead
| t_primary genexp &t_lookahead
| t_primary '(' [arguments] ')' &t_lookahead
| atom &t_lookahead
t_lookahead: '(' | '[' | '.'
# Targets for del statements
# --------------------------
del_targets: ','.del_target+ [',']
del_target:
| t_primary '.' NAME !t_lookahead
| t_primary '[' slices ']' !t_lookahead
| del_t_atom
del_t_atom:
| NAME
| '(' del_target ')'
| '(' [del_targets] ')'
| '[' [del_targets] ']'
# TYPING ELEMENTS
# ---------------
# type_expressions allow */** but ignore them
type_expressions:
| ','.expression+ ',' '*' expression ',' '**' expression
| ','.expression+ ',' '*' expression
| ','.expression+ ',' '**' expression
| '*' expression ',' '**' expression
| '*' expression
| '**' expression
| ','.expression+
func_type_comment:
| NEWLINE TYPE_COMMENT &(NEWLINE INDENT) # Must be followed by indented block
| TYPE_COMMENT
# ========================= END OF THE GRAMMAR ===========================
# ========================= START OF INVALID RULES =======================