Nota
¡Ayúdanos a traducir la documentación oficial de Python al Español! Puedes encontrar más información en Como contribuir. Ayuda a acercar Python a más personas de habla hispana.
10. Especificación completa de la gramática¶
Esta es la gramática completa de Python, derivada directamente de la gramática utilizada para generar el analizador CPython (ver Grammar/python.gram). La versión aquí omite detalles relacionados con la generación de código y la recuperación de errores.
The notation is a mixture of EBNF
and PEG.
In particular, &
followed by a symbol, token or parenthesized
group indicates a positive lookahead (i.e., is required to match but
not consumed), while !
indicates a negative lookahead (i.e., is
required not to match). We use the |
separator to mean PEG’s
«ordered choice» (written as /
in traditional PEG grammars). See
PEP 617 for more details on the grammar’s syntax.
# 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
fstring: star_expressions
# 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 ":" expression
| '*' NAME
| '**' NAME ":" expression
| '**' 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 =======================