python / python/cpython

`ast.class._field_types` causes Exception when `ast.class._fields` does not cause Exception

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描述

Bug report

Bug description:

_field and _field_types behave differently

Accessing the _field_types attribute of an ast.AST subclass will cause an exception if the class has no _fields, but accessing the _fields attribute never causes an exception.

Example: ast.mod

(.venv) C:\clones\cpython>py
Python 3.13.5 (tags/v3.13.5:6cb20a2, Jun 11 2025, 16:15:46) [MSC v.1943 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import ast
>>> ast.mod._fields
()
>>> ast.mod._field_types
Traceback (most recent call last):
  File "<python-input-2>", line 1, in <module>
    ast.mod._field_types
AttributeError: type object 'mod' has no attribute '_field_types'
>>>

_field and _field_types for all ast.AST subclasses

Details 

(.venv) C:\clones\cpython>C:\clones\cpython\.venv\Scripts\python.exe c:/clones/cpython/field_types.py
3.13.5 (tags/v3.13.5:6cb20a2, Jun 11 2025, 16:15:46) [MSC v.1943 64 bit (AMD64)]

astClass._fields
AST ()
mod ()
stmt ()
expr ()
expr_context ()
boolop ()
operator ()
unaryop ()
cmpop ()
comprehension ('target', 'iter', 'ifs', 'is_async')
excepthandler ()
arguments ('posonlyargs', 'args', 'vararg', 'kwonlyargs', 'kw_defaults', 'kwarg', 'defaults')
arg ('arg', 'annotation', 'type_comment')
keyword ('arg', 'value')
alias ('name', 'asname')
withitem ('context_expr', 'optional_vars')
match_case ('pattern', 'guard', 'body')
pattern ()
type_ignore ()
type_param ()
slice ()
Num ('n',)
Str ('s',)
Bytes ('s',)
NameConstant ('value', 'kind')
Ellipsis ()
Module ('body', 'type_ignores')
Interactive ('body',)
Expression ('body',)
FunctionType ('argtypes', 'returns')
Suite ()
FunctionDef ('name', 'args', 'body', 'decorator_list', 'returns', 'type_comment', 'type_params')
AsyncFunctionDef ('name', 'args', 'body', 'decorator_list', 'returns', 'type_comment', 'type_params')
ClassDef ('name', 'bases', 'keywords', 'body', 'decorator_list', 'type_params')
Return ('value',)
Delete ('targets',)
Assign ('targets', 'value', 'type_comment')
TypeAlias ('name', 'type_params', 'value')
AugAssign ('target', 'op', 'value')
AnnAssign ('target', 'annotation', 'value', 'simple')
For ('target', 'iter', 'body', 'orelse', 'type_comment')
AsyncFor ('target', 'iter', 'body', 'orelse', 'type_comment')
While ('test', 'body', 'orelse')
If ('test', 'body', 'orelse')
With ('items', 'body', 'type_comment')
AsyncWith ('items', 'body', 'type_comment')
Match ('subject', 'cases')
Raise ('exc', 'cause')
Try ('body', 'handlers', 'orelse', 'finalbody')
TryStar ('body', 'handlers', 'orelse', 'finalbody')
Assert ('test', 'msg')
Import ('names',)
ImportFrom ('module', 'names', 'level')
Global ('names',)
Nonlocal ('names',)
Expr ('value',)
Pass ()
Break ()
Continue ()
BoolOp ('op', 'values')
NamedExpr ('target', 'value')
BinOp ('left', 'op', 'right')
UnaryOp ('op', 'operand')
Lambda ('args', 'body')
IfExp ('test', 'body', 'orelse')
Dict ('keys', 'values')
Set ('elts',)
ListComp ('elt', 'generators')
SetComp ('elt', 'generators')
DictComp ('key', 'value', 'generators')
GeneratorExp ('elt', 'generators')
Await ('value',)
Yield ('value',)
YieldFrom ('value',)
Compare ('left', 'ops', 'comparators')
Call ('func', 'args', 'keywords')
FormattedValue ('value', 'conversion', 'format_spec')
JoinedStr ('values',)
Constant ('value', 'kind')
Attribute ('value', 'attr', 'ctx')
Subscript ('value', 'slice', 'ctx')
Starred ('value', 'ctx')
Name ('id', 'ctx')
List ('elts', 'ctx')
Tuple ('elts', 'ctx')
Slice ('lower', 'upper', 'step')
Load ()
Store ()
Del ()
AugLoad ()
AugStore ()
Param ()
And ()
Or ()
Add ()
Sub ()
Mult ()
MatMult ()
Div ()
Mod ()
Pow ()
LShift ()
RShift ()
BitOr ()
BitXor ()
BitAnd ()
FloorDiv ()
Invert ()
Not ()
UAdd ()
USub ()
Eq ()
NotEq ()
Lt ()
LtE ()
Gt ()
GtE ()
Is ()
IsNot ()
In ()
NotIn ()
ExceptHandler ('type', 'name', 'body')
MatchValue ('value',)
MatchSingleton ('value',)
MatchSequence ('patterns',)
MatchMapping ('keys', 'patterns', 'rest')
MatchClass ('cls', 'patterns', 'kwd_attrs', 'kwd_patterns')
MatchStar ('name',)
MatchAs ('pattern', 'name')
MatchOr ('patterns',)
TypeIgnore ('lineno', 'tag')
TypeVar ('name', 'bound', 'default_value')
ParamSpec ('name', 'default_value')
TypeVarTuple ('name', 'default_value')
Index ()
ExtSlice ()
countExceptions = 0

astClass._field_types
AttributeError: AST
AttributeError: mod
AttributeError: stmt
AttributeError: expr
AttributeError: expr_context
AttributeError: boolop
AttributeError: operator
AttributeError: unaryop
AttributeError: cmpop
comprehension {'target': <class 'ast.expr'>, 'iter': <class 'ast.expr'>, 'ifs': list[ast.expr], 'is_async': <class 'int'>}
AttributeError: excepthandler
arguments {'posonlyargs': list[ast.arg], 'args': list[ast.arg], 'vararg': ast.arg | None, 'kwonlyargs': list[ast.arg], 'kw_defaults': list[ast.expr], 'kwarg': ast.arg | None, 'defaults': list[ast.expr]}
arg {'arg': <class 'str'>, 'annotation': ast.expr | None, 'type_comment': str | None}
keyword {'arg': str | None, 'value': <class 'ast.expr'>}
alias {'name': <class 'str'>, 'asname': str | None}
withitem {'context_expr': <class 'ast.expr'>, 'optional_vars': ast.expr | None}
match_case {'pattern': <class 'ast.pattern'>, 'guard': ast.expr | None, 'body': list[ast.stmt]}
AttributeError: pattern
AttributeError: type_ignore
AttributeError: type_param
AttributeError: slice
Num {'value': <class 'object'>, 'kind': str | None}
Str {'value': <class 'object'>, 'kind': str | None}
Bytes {'value': <class 'object'>, 'kind': str | None}
NameConstant {'value': <class 'object'>, 'kind': str | None}
Ellipsis {'value': <class 'object'>, 'kind': str | None}
Module {'body': list[ast.stmt], 'type_ignores': list[ast.type_ignore]}
Interactive {'body': list[ast.stmt]}
Expression {'body': <class 'ast.expr'>}
FunctionType {'argtypes': list[ast.expr], 'returns': <class 'ast.expr'>}
AttributeError: Suite
FunctionDef {'name': <class 'str'>, 'args': <class 'ast.arguments'>, 'body': list[ast.stmt], 'decorator_list': list[ast.expr], 'returns': ast.expr | None, 'type_comment': str | None, 'type_params': list[ast.type_param]}
AsyncFunctionDef {'name': <class 'str'>, 'args': <class 'ast.arguments'>, 'body': list[ast.stmt], 'decorator_list': list[ast.expr], 'returns': ast.expr | None, 'type_comment': str | None, 'type_params': list[ast.type_param]}
ClassDef {'name': <class 'str'>, 'bases': list[ast.expr], 'keywords': list[ast.keyword], 'body': list[ast.stmt], 'decorator_list': list[ast.expr], 'type_params': list[ast.type_param]}
Return {'value': ast.expr | None}
Delete {'targets': list[ast.expr]}
Assign {'targets': list[ast.expr], 'value': <class 'ast.expr'>, 'type_comment': str | None}
TypeAlias {'name': <class 'ast.expr'>, 'type_params': list[ast.type_param], 'value': <class 'ast.expr'>}
AugAssign {'target': <class 'ast.expr'>, 'op': <class 'ast.operator'>, 'value': <class 'ast.expr'>}
AnnAssign {'target': <class 'ast.expr'>, 'annotation': <class 'ast.expr'>, 'value': ast.expr | None, 'simple': <class 'int'>}
For {'target': <class 'ast.expr'>, 'iter': <class 'ast.expr'>, 'body': list[ast.stmt], 'orelse': list[ast.stmt], 'type_comment': str | None}
AsyncFor {'target': <class 'ast.expr'>, 'iter': <class 'ast.expr'>, 'body': list[ast.stmt], 'orelse': list[ast.stmt], 'type_comment': str | None}
While {'test': <class 'ast.expr'>, 'body': list[ast.stmt], 'orelse': list[ast.stmt]}
If {'test': <class 'ast.expr'>, 'body': list[ast.stmt], 'orelse': list[ast.stmt]}
With {'items': list[ast.withitem], 'body': list[ast.stmt], 'type_comment': str | None}
AsyncWith {'items': list[ast.withitem], 'body': list[ast.stmt], 'type_comment': str | None}
Match {'subject': <class 'ast.expr'>, 'cases': list[ast.match_case]}
Raise {'exc': ast.expr | None, 'cause': ast.expr | None}
Try {'body': list[ast.stmt], 'handlers': list[ast.excepthandler], 'orelse': list[ast.stmt], 'finalbody': list[ast.stmt]}
TryStar {'body': list[ast.stmt], 'handlers': list[ast.excepthandler], 'orelse': list[ast.stmt], 'finalbody': list[ast.stmt]}
Assert {'test': <class 'ast.expr'>, 'msg': ast.expr | None}
Import {'names': list[ast.alias]}
ImportFrom {'module': str | None, 'names': list[ast.alias], 'level': int | None}
Global {'names': list[str]}
Nonlocal {'names': list[str]}
Expr {'value': <class 'ast.expr'>}
Pass {}
Break {}
Continue {}
BoolOp {'op': <class 'ast.boolop'>, 'values': list[ast.expr]}
NamedExpr {'target': <class 'ast.expr'>, 'value': <class 'ast.expr'>}
BinOp {'left': <class 'ast.expr'>, 'op': <class 'ast.operator'>, 'right': <class 'ast.expr'>}
UnaryOp {'op': <class 'ast.unaryop'>, 'operand': <class 'ast.expr'>}
Lambda {'args': <class 'ast.arguments'>, 'body': <class 'ast.expr'>}
IfExp {'test': <class 'ast.expr'>, 'body': <class 'ast.expr'>, 'orelse': <class 'ast.expr'>}
Dict {'keys': list[ast.expr], 'values': list[ast.expr]}
Set {'elts': list[ast.expr]}
ListComp {'elt': <class 'ast.expr'>, 'generators': list[ast.comprehension]}
SetComp {'elt': <class 'ast.expr'>, 'generators': list[ast.comprehension]}
DictComp {'key': <class 'ast.expr'>, 'value': <class 'ast.expr'>, 'generators': list[ast.comprehension]}
GeneratorExp {'elt': <class 'ast.expr'>, 'generators': list[ast.comprehension]}
Await {'value': <class 'ast.expr'>}
Yield {'value': ast.expr | None}
YieldFrom {'value': <class 'ast.expr'>}
Compare {'left': <class 'ast.expr'>, 'ops': list[ast.cmpop], 'comparators': list[ast.expr]}
Call {'func': <class 'ast.expr'>, 'args': list[ast.expr], 'keywords': list[ast.keyword]}
FormattedValue {'value': <class 'ast.expr'>, 'conversion': <class 'int'>, 'format_spec': ast.expr | None}
JoinedStr {'values': list[ast.expr]}
Constant {'value': <class 'object'>, 'kind': str | None}
Attribute {'value': <class 'ast.expr'>, 'attr': <class 'str'>, 'ctx': <class 'ast.expr_context'>}
Subscript {'value': <class 'ast.expr'>, 'slice': <class 'ast.expr'>, 'ctx': <class 'ast.expr_context'>}
Starred {'value': <class 'ast.expr'>, 'ctx': <class 'ast.expr_context'>}
Name {'id': <class 'str'>, 'ctx': <class 'ast.expr_context'>}
List {'elts': list[ast.expr], 'ctx': <class 'ast.expr_context'>}
Tuple {'elts': list[ast.expr], 'ctx': <class 'ast.expr_context'>}
Slice {'lower': ast.expr | None, 'upper': ast.expr | None, 'step': ast.expr | None}
Load {}
Store {}
Del {}
AttributeError: AugLoad
AttributeError: AugStore
AttributeError: Param
And {}
Or {}
Add {}
Sub {}
Mult {}
MatMult {}
Div {}
Mod {}
Pow {}
LShift {}
RShift {}
BitOr {}
BitXor {}
BitAnd {}
FloorDiv {}
Invert {}
Not {}
UAdd {}
USub {}
Eq {}
NotEq {}
Lt {}
LtE {}
Gt {}
GtE {}
Is {}
IsNot {}
In {}
NotIn {}
ExceptHandler {'type': ast.expr | None, 'name': str | None, 'body': list[ast.stmt]}
MatchValue {'value': <class 'ast.expr'>}
MatchSingleton {'value': <class 'object'>}
MatchSequence {'patterns': list[ast.pattern]}
MatchMapping {'keys': list[ast.expr], 'patterns': list[ast.pattern], 'rest': str | None}
MatchClass {'cls': <class 'ast.expr'>, 'patterns': list[ast.pattern], 'kwd_attrs': list[str], 'kwd_patterns': list[ast.pattern]}
MatchStar {'name': str | None}
MatchAs {'pattern': ast.pattern | None, 'name': str | None}
MatchOr {'patterns': list[ast.pattern]}
TypeIgnore {'lineno': <class 'int'>, 'tag': <class 'str'>}
TypeVar {'name': <class 'str'>, 'bound': ast.expr | None, 'default_value': ast.expr | None}
ParamSpec {'name': <class 'str'>, 'default_value': ast.expr | None}
TypeVarTuple {'name': <class 'str'>, 'default_value': ast.expr | None}
AttributeError: Index
AttributeError: ExtSlice
countExceptions = 20

No errors after code changes

After adding logic to "Parser/asdl_c.py" to treat _field_types similar to _fields, the exceptions were replaced with empty dictionaries.

Summary

(.venv) C:\clones\cpython>C:\clones\cpython\python c:/clones/cpython/field_types.py
Running Debug|x64 interpreter...
3.15.0a0 (heads/main-dirty:b14986c9146, Jun 21 2025, 15:02:00) [MSC v.1944 64 bit (AMD64)]

astClass._fields
countExceptions = 0

astClass._field_types
countExceptions = 0

_field_types for all ast.AST subclasses

Details 

AST {}
mod {}
stmt {}
expr {}
expr_context {}
boolop {}
operator {}
unaryop {}
cmpop {}
comprehension {'target': <class 'ast.expr'>, 'iter': <class 'ast.expr'>, 'ifs': list[ast.expr], 'is_async': <class 'int'>}
excepthandler {}
arguments {'posonlyargs': list[ast.arg], 'args': list[ast.arg], 'vararg': ast.arg | None, 'kwonlyargs': list[ast.arg], 'kw_defaults': list[ast.expr], 'kwarg': ast.arg | None, 'defaults': list[ast.expr]}
arg {'arg': <class 'str'>, 'annotation': ast.expr | None, 'type_comment': str | None}
keyword {'arg': str | None, 'value': <class 'ast.expr'>}
alias {'name': <class 'str'>, 'asname': str | None}
withitem {'context_expr': <class 'ast.expr'>, 'optional_vars': ast.expr | None}
match_case {'pattern': <class 'ast.pattern'>, 'guard': ast.expr | None, 'body': list[ast.stmt]}
pattern {}
type_ignore {}
type_param {}
slice {}
Module {'body': list[ast.stmt], 'type_ignores': list[ast.type_ignore]}
Interactive {'body': list[ast.stmt]}
Expression {'body': <class 'ast.expr'>}
FunctionType {'argtypes': list[ast.expr], 'returns': <class 'ast.expr'>}
Suite {}
FunctionDef {'name': <class 'str'>, 'args': <class 'ast.arguments'>, 'body': list[ast.stmt], 'decorator_list': list[ast.expr], 'returns': ast.expr | None, 'type_comment': str | None, 'type_params': list[ast.type_param]}
AsyncFunctionDef {'name': <class 'str'>, 'args': <class 'ast.arguments'>, 'body': list[ast.stmt], 'decorator_list': list[ast.expr], 'returns': ast.expr | None, 'type_comment': str | None, 'type_params': list[ast.type_param]}
ClassDef {'name': <class 'str'>, 'bases': list[ast.expr], 'keywords': list[ast.keyword], 'body': list[ast.stmt], 'decorator_list': list[ast.expr], 'type_params': list[ast.type_param]}
Return {'value': ast.expr | None}
Delete {'targets': list[ast.expr]}
Assign {'targets': list[ast.expr], 'value': <class 'ast.expr'>, 'type_comment': str | None}
TypeAlias {'name': <class 'ast.expr'>, 'type_params': list[ast.type_param], 'value': <class 'ast.expr'>}
AugAssign {'target': <class 'ast.expr'>, 'op': <class 'ast.operator'>, 'value': <class 'ast.expr'>}
AnnAssign {'target': <class 'ast.expr'>, 'annotation': <class 'ast.expr'>, 'value': ast.expr | None, 'simple': <class 'int'>}
For {'target': <class 'ast.expr'>, 'iter': <class 'ast.expr'>, 'body': list[ast.stmt], 'orelse': list[ast.stmt], 'type_comment': str | None}
AsyncFor {'target': <class 'ast.expr'>, 'iter': <class 'ast.expr'>, 'body': list[ast.stmt], 'orelse': list[ast.stmt], 'type_comment': str | None}
While {'test': <class 'ast.expr'>, 'body': list[ast.stmt], 'orelse': list[ast.stmt]}
If {'test': <class 'ast.expr'>, 'body': list[ast.stmt], 'orelse': list[ast.stmt]}
With {'items': list[ast.withitem], 'body': list[ast.stmt], 'type_comment': str | None}
AsyncWith {'items': list[ast.withitem], 'body': list[ast.stmt], 'type_comment': str | None}
Match {'subject': <class 'ast.expr'>, 'cases': list[ast.match_case]}
Raise {'exc': ast.expr | None, 'cause': ast.expr | None}
Try {'body': list[ast.stmt], 'handlers': list[ast.excepthandler], 'orelse': list[ast.stmt], 'finalbody': list[ast.stmt]}
TryStar {'body': list[ast.stmt], 'handlers': list[ast.excepthandler], 'orelse': list[ast.stmt], 'finalbody': list[ast.stmt]}
Assert {'test': <class 'ast.expr'>, 'msg': ast.expr | None}
Import {'names': list[ast.alias]}
ImportFrom {'module': str | None, 'names': list[ast.alias], 'level': int | None}
Global {'names': list[str]}
Nonlocal {'names': list[str]}
Expr {'value': <class 'ast.expr'>}
Pass {}
Break {}
Continue {}
BoolOp {'op': <class 'ast.boolop'>, 'values': list[ast.expr]}
NamedExpr {'target': <class 'ast.expr'>, 'value': <class 'ast.expr'>}
BinOp {'left': <class 'ast.expr'>, 'op': <class 'ast.operator'>, 'right': <class 'ast.expr'>}
UnaryOp {'op': <class 'ast.unaryop'>, 'operand': <class 'ast.expr'>}
Lambda {'args': <class 'ast.arguments'>, 'body': <class 'ast.expr'>}
IfExp {'test': <class 'ast.expr'>, 'body': <class 'ast.expr'>, 'orelse': <class 'ast.expr'>}
Dict {'keys': list[ast.expr], 'values': list[ast.expr]}
Set {'elts': list[ast.expr]}
ListComp {'elt': <class 'ast.expr'>, 'generators': list[ast.comprehension]}
SetComp {'elt': <class 'ast.expr'>, 'generators': list[ast.comprehension]}
DictComp {'key': <class 'ast.expr'>, 'value': <class 'ast.expr'>, 'generators': list[ast.comprehension]}
GeneratorExp {'elt': <class 'ast.expr'>, 'generators': list[ast.comprehension]}
Await {'value': <class 'ast.expr'>}
Yield {'value': ast.expr | None}
YieldFrom {'value': <class 'ast.expr'>}
Compare {'left': <class 'ast.expr'>, 'ops': list[ast.cmpop], 'comparators': list[ast.expr]}
Call {'func': <class 'ast.expr'>, 'args': list[ast.expr], 'keywords': list[ast.keyword]}
FormattedValue {'value': <class 'ast.expr'>, 'conversion': <class 'int'>, 'format_spec': ast.expr | None}
Interpolation {'value': <class 'ast.expr'>, 'str': <class 'object'>, 'conversion': <class 'int'>, 'format_spec': ast.expr | None}
JoinedStr {'values': list[ast.expr]}
TemplateStr {'values': list[ast.expr]}
Constant {'value': <class 'object'>, 'kind': str | None}
Attribute {'value': <class 'ast.expr'>, 'attr': <class 'str'>, 'ctx': <class 'ast.expr_context'>}
Subscript {'value': <class 'ast.expr'>, 'slice': <class 'ast.expr'>, 'ctx': <class 'ast.expr_context'>}
Starred {'value': <class 'ast.expr'>, 'ctx': <class 'ast.expr_context'>}
Name {'id': <class 'str'>, 'ctx': <class 'ast.expr_context'>}
List {'elts': list[ast.expr], 'ctx': <class 'ast.expr_context'>}
Tuple {'elts': list[ast.expr], 'ctx': <class 'ast.expr_context'>}
Slice {'lower': ast.expr | None, 'upper': ast.expr | None, 'step': ast.expr | None}
Load {}
Store {}
Del {}
AugLoad {}
AugStore {}
Param {}
And {}
Or {}
Add {}
Sub {}
Mult {}
MatMult {}
Div {}
Mod {}
Pow {}
LShift {}
RShift {}
BitOr {}
BitXor {}
BitAnd {}
FloorDiv {}
Invert {}
Not {}
UAdd {}
USub {}
Eq {}
NotEq {}
Lt {}
LtE {}
Gt {}
GtE {}
Is {}
IsNot {}
In {}
NotIn {}
ExceptHandler {'type': ast.expr | None, 'name': str | None, 'body': list[ast.stmt]}
MatchValue {'value': <class 'ast.expr'>}
MatchSingleton {'value': <class 'object'>}
MatchSequence {'patterns': list[ast.pattern]}
MatchMapping {'keys': list[ast.expr], 'patterns': list[ast.pattern], 'rest': str | None}
MatchClass {'cls': <class 'ast.expr'>, 'patterns': list[ast.pattern], 'kwd_attrs': list[str], 'kwd_patterns': list[ast.pattern]}
MatchStar {'name': str | None}
MatchAs {'pattern': ast.pattern | None, 'name': str | None}
MatchOr {'patterns': list[ast.pattern]}
TypeIgnore {'lineno': <class 'int'>, 'tag': <class 'str'>}
TypeVar {'name': <class 'str'>, 'bound': ast.expr | None, 'default_value': ast.expr | None}
ParamSpec {'name': <class 'str'>, 'default_value': ast.expr | None}
TypeVarTuple {'name': <class 'str'>, 'default_value': ast.expr | None}
Index {}
ExtSlice {}
countExceptions = 0

Check for errors on branches

Not applicable to 3.9, 3.10, 3.11, 3.12.

Branch 3.13

Details 

(.venv) C:\clones\cpython>C:\clones\cpython\python c:/clones/cpython/field_types.py
Running Debug|x64 interpreter...
3.13.5+ (heads/3.13:4eab9da960d, Jun 21 2025, 14:44:53) [MSC v.1944 64 bit (AMD64)]

astClass._fields
countExceptions = 0

astClass._field_types
AttributeError: AST
AttributeError: mod
AttributeError: stmt
AttributeError: expr
AttributeError: expr_context
AttributeError: boolop
AttributeError: operator
AttributeError: unaryop
AttributeError: cmpop
AttributeError: excepthandler
AttributeError: pattern
AttributeError: type_ignore
AttributeError: type_param
AttributeError: slice
AttributeError: Suite
AttributeError: AugLoad
AttributeError: AugStore
AttributeError: Param
AttributeError: Index
AttributeError: ExtSlice
countExceptions = 20

Branch 3.14

Details 

(.venv) C:\clones\cpython>C:\clones\cpython\python c:/clones/cpython/field_types.py
Running Debug|x64 interpreter...
3.14.0b3+ (heads/3.14:73e2089ed13, Jun 21 2025, 14:57:19) [MSC v.1944 64 bit (AMD64)]

astClass._fields
countExceptions = 0

astClass._field_types
AttributeError: AST
AttributeError: mod
AttributeError: stmt
AttributeError: expr
AttributeError: expr_context
AttributeError: boolop
AttributeError: operator
AttributeError: unaryop
AttributeError: cmpop
AttributeError: excepthandler
AttributeError: pattern
AttributeError: type_ignore
AttributeError: type_param
AttributeError: slice
AttributeError: Suite
AttributeError: AugLoad
AttributeError: AugStore
AttributeError: Param
AttributeError: Index
AttributeError: ExtSlice
countExceptions = 20

Branch main

Details 

(.venv) C:\clones\cpython>C:\clones\cpython\python c:/clones/cpython/field_types.py
Running Debug|x64 interpreter...
3.15.0a0 (heads/main:b14986c9146, Jun 21 2025, 14:59:45) [MSC v.1944 64 bit (AMD64)]

astClass._fields
countExceptions = 0

astClass._field_types
AttributeError: AST
AttributeError: mod
AttributeError: stmt
AttributeError: expr
AttributeError: expr_context
AttributeError: boolop
AttributeError: operator
AttributeError: unaryop
AttributeError: cmpop
AttributeError: excepthandler
AttributeError: pattern
AttributeError: type_ignore
AttributeError: type_param
AttributeError: slice
AttributeError: Suite
AttributeError: AugLoad
AttributeError: AugStore
AttributeError: Param
AttributeError: Index
AttributeError: ExtSlice
countExceptions = 20

Python code used to generate the above tests

Details 

from itertools import chain
import ast
import sys

print(sys.version, end='\n\n')

countExceptions = 0
print('astClass._fields')
for astClass in [C for C in [ast.AST,*chain(*(c.__subclasses__() for c in [ast.AST,ast.Constant,*ast.AST.__subclasses__()]))] if issubclass(C,ast.AST)]:
	try:
		print(astClass.__name__, astClass._fields)
		# astClass._fields
	except AttributeError as ERRORmessage:
		print(ERRORmessage.__class__.__name__, astClass.__name__, sep=': ')
		countExceptions += 1
print(f"{countExceptions = }\n")

countExceptions = 0
print('astClass._field_types')
for astClass in [C for C in [ast.AST,*chain(*(c.__subclasses__() for c in [ast.AST,ast.Constant,*ast.AST.__subclasses__()]))] if issubclass(C,ast.AST)]:
	try:
		print(astClass.__name__, astClass._field_types)
		# astClass._field_types
	except AttributeError as ERRORmessage:
		print(ERRORmessage.__class__.__name__, astClass.__name__, sep=': ')
		countExceptions += 1
print(f"{countExceptions = }")

CPython versions tested on:

3.13, 3.14, CPython main branch

Operating systems tested on:

Windows

Linked PRs
  • gh-135800

贡献指南

打开贡献指南

从这里开始

  1. 先读完整个 Issue，再读项目的贡献指南。
  2. 在 Issue 下留言说明你要接手 —— 这能避免两个人做同样的事。
  3. Fork 仓库，在一个分支上完成修改。
  4. 提交 Pull Request，并在描述里引用这个 Issue 编号。

调研方向

从 Parser/asdl_c.py 开始，issue 中提到要添加逻辑，使 _field_types 按照 _fields 进行处理。使用受影响的解释器运行提到的 field_types.py 脚本，并比较有字段和无字段的 AST 子类。完成的标准是：报告的 AttributeError 情况被替换为空字典，且脚本输出中没有错误。

由索引模型根据 Issue 内容生成。

评估

技术栈
python
领域
compilers
Issue 类型
缺陷
难度
3/5
预计耗时
1-2 天
活跃度
停滞
描述清晰度
基本清楚
新手友好度
35/100

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