Python 3.12 Feature Checklist¶

Document Purpose: Map all Python 3.12 syntax forms to multilingual language implementation status.

Last Updated: 2026-02-22 | Target Coverage: 100% | Current Coverage: 95%+

Core Language Features¶

Literals & Constants¶

Feature	Status	Notes	Test File
Integer literals (decimal, hex, octal, binary)	✅ Supported	Including Unicode numerals	`test_literals`
Float literals (including scientific notation)	✅ Supported	1.5e10, 1.5e-10	`test_literals`
String literals (single, double, triple-quoted)	✅ Supported	All quote variants	`test_string_literals`
F-strings (basic)	✅ Supported	`f"{x}"`	`test_fstrings_basic`
F-string format specs	✅ Supported	`f"{x:.2f}"`, `f"{x!r}"`, `f"{x!s}"`, `f"{x!a}"`	`test_fstrings_format_specs`
Complex numbers	✅ Supported	`1+2j`	`test_complex_literals`
Boolean literals	✅ Supported	`True`, `False`	`test_boolean_literals`
None literal	✅ Supported	`None`	`test_none_literal`
Bytes literals	⚠️ Partial	Not explicitly tested	`PENDING`
Raw strings	✅ Supported	`r"..."`	`test_raw_strings`

Operators¶

Arithmetic¶

Operator	Status	Notes	Test File
`+`, `-`, `*`, `/`	✅ Supported	Basic arithmetic	`test_arithmetic_ops`
`//`, `%`	✅ Supported	Floor division, modulo	`test_arithmetic_ops`
`**`	✅ Supported	Exponentiation	`test_arithmetic_ops`
Unary `+`, `-`	✅ Supported	Unary operators	`test_unary_ops`

Comparison¶

Operator	Status	Notes	Test File
`==`, `!=`, `<`, `>`, `<=`, `>=`	✅ Supported	All comparison operators	`test_comparison_ops`
Chained comparisons	✅ Supported	`a < b < c`	`test_chained_comparisons`
`in`, `not in`	✅ Supported	Membership testing	`test_membership_ops`
`is`, `is not`	✅ Supported	Identity testing	`test_identity_ops`

Logical¶

Operator	Status	Notes	Test File
`and`, `or`, `not`	✅ Supported	Boolean operators	`test_logical_ops`
Short-circuit evaluation	✅ Supported	Verified in differential tests	`differential_312_test.py`

Bitwise¶

Operator	Status	Notes	Test File
`&`, `\|`, `^`	✅ Supported	Bitwise AND, OR, XOR	`test_bitwise_ops`
`~`	✅ Supported	Bitwise NOT	`test_bitwise_ops`
`<<`, `>>`	✅ Supported	Bit shifts	`test_bitwise_ops`

Assignment¶

Operator	Status	Notes	Test File
`=`	✅ Supported	Basic assignment	`test_assignment`
`+=`, `-=`, `*=`, `/=`	✅ Supported	Basic augmented assignment	`test_augmented_assignment`
`**=`, `//=`, `%=`	✅ Supported	Advanced augmented ops	`test_augmented_assignment`
`&=`, `\|=`, `^=`, `<<=`, `>>=`	✅ Supported	Bitwise augmented ops	`test_augmented_assignment`
`:=` (Walrus)	✅ Supported	Named expressions	`test_walrus_operator`

Special¶

Operator	Status	Notes	Test File
`**kwargs`	✅ Supported	Dictionary unpacking	`test_dict_unpacking`
`*args`	✅ Supported	Iterable unpacking	`test_iterable_unpacking`
`.` (attribute access)	✅ Supported	Dot notation	`test_attribute_access`
`[]` (indexing)	✅ Supported	Index access	`test_indexing`
`[:]` (slicing)	✅ Supported	Slice notation with start:stop:step	`test_slicing`

Variables & Assignments¶

Feature	Status	Notes	Test File
Variable assignment	✅ Supported	`x = 10`	`test_assignment`
Multiple assignment	✅ Supported	`x, y = 1, 2`	`test_multiple_assignment`
Tuple unpacking	✅ Supported	`a, b = [1, 2]`	`test_tuple_unpacking`
Starred unpacking	✅ Supported	`a, *rest, b = [1,2,3,4,5]`	`test_starred_unpacking`
Chained assignment	✅ Supported	`a = b = c = 0`	`test_chained_assignment`
Type annotations	✅ Supported	`x: int = 10`	`test_type_annotations`
Variable deletion	✅ Supported	`del x`	`test_del_statement`

Control Flow¶

Conditional Statements¶

Feature	Status	Notes	Test File
`if` statement	✅ Supported	Single condition	`test_if_statement`
`if/elif/else`	✅ Supported	Multiple branches	`test_if_elif_else`
Ternary expression	✅ Supported	`x if cond else y`	`test_ternary_expression`

Loop Statements¶

Feature	Status	Notes	Test File
`while` loop	✅ Supported	While loops	`test_while_loop`
`while/else`	✅ Supported	Else block when no break	`test_while_else`
`for` loop	✅ Supported	Iteration	`test_for_loop`
`for/else`	✅ Supported	Else block when no break	`test_for_else`
`break` statement	✅ Supported	Exit loop	`test_break_statement`
`continue` statement	✅ Supported	Skip to next iteration	`test_continue_statement`
`pass` statement	✅ Supported	No-op placeholder	`test_pass_statement`

Exception Handling¶

Feature	Status	Notes	Test File
`try/except`	✅ Supported	Exception catching	`test_try_except`
Multiple `except` handlers	✅ Supported	Catch different exceptions	`test_multiple_except`
`except` with `as`	✅ Supported	Bind exception to variable	`test_except_as`
`try/except/else`	✅ Supported	Else if no exception	`test_try_except_else`
`try/except/finally`	✅ Supported	Cleanup block	`test_try_finally`
`try/except/else/finally`	✅ Supported	All combinations	`test_try_all`
`raise` statement	✅ Supported	Raise exceptions	`test_raise_statement`
`raise ... from ...`	✅ Supported	Exception chaining	`test_exception_chaining`

Functions¶

Function Definition¶

Feature	Status	Notes	Test File
Basic function def	✅ Supported	`def f(): pass`	`test_function_def`
Parameters	✅ Supported	`def f(x, y):`	`test_function_params`
Default parameters	✅ Supported	`def f(x=10):`	`test_default_params`
`*args`	✅ Supported	Variable positional args	`test_varargs`
`**kwargs`	✅ Supported	Variable keyword args	`test_kwargs`
Positional-only params	✅ Supported	`def f(x, /, y):` (PEP 570)	`test_positional_only`
Keyword-only params	✅ Supported	`def f(*, x):`	`test_keyword_only`
Type hints (params)	✅ Supported	`def f(x: int):`	`test_param_type_hints`
Type hints (return)	✅ Supported	`def f() -> int:`	`test_return_type_hints`
Decorators	✅ Supported	`@decorator`	`test_decorators`
Multiple decorators	✅ Supported	Stacked decorators	`test_multiple_decorators`
Docstrings	✅ Supported	Triple-quoted documentation	`test_docstrings`

Function Calls¶

Feature	Status	Notes	Test File
Positional arguments	✅ Supported	`f(1, 2)`	`test_function_call`
Keyword arguments	✅ Supported	`f(x=1, y=2)`	`test_keyword_args`
Mixed arguments	✅ Supported	`f(1, y=2)`	`test_mixed_args`
`*args` unpacking	✅ Supported	`f(*[1,2])`	`test_args_unpacking`
`**kwargs` unpacking	✅ Supported	`f(**{"x":1})`	`test_kwargs_unpacking`

Return Statements¶

Feature	Status	Notes	Test File
`return` (no value)	✅ Supported	Return None	`test_return_none`
`return value`	✅ Supported	Return single value	`test_return_value`
`return` multiple values	✅ Supported	Tuple return	`test_return_tuple`

Special Functions¶

Feature	Status	Notes	Test File
`lambda` expressions	✅ Supported	Anonymous functions	`test_lambda`
Generator functions	✅ Supported	`yield` statement	`test_generators`
`yield` expression	✅ Supported	`yield value`	`test_yield_expression`
`yield from`	✅ Supported	`yield from iterable`	`test_yield_from`
Async functions	✅ Supported	`async def`	`test_async_def`
`await` expression	✅ Supported	`await async_call()`	`test_await`

Classes¶

Class Definition¶

Feature	Status	Notes	Test File
Basic class	✅ Supported	`class C: pass`	`test_class_def`
Class with inheritance	✅ Supported	`class C(Parent):`	`test_class_inheritance`
Multiple inheritance	✅ Supported	`class C(P1, P2):`	`test_multiple_inheritance`
Class decorators	✅ Supported	`@decorator class C:`	`test_class_decorators`
Class variables	✅ Supported	Class-level attributes	`test_class_variables`
Instance variables	✅ Supported	`self.attr = value`	`test_instance_variables`
Methods	✅ Supported	`def method(self):`	`test_methods`
Static methods	✅ Supported	`@staticmethod`	`test_static_methods`
Class methods	✅ Supported	`@classmethod`	`test_class_methods`
Properties	✅ Supported	`@property`	`test_properties`
`__init__` method	✅ Supported	Constructor	`test_init`
`super()`	✅ Supported	Call parent methods	`test_super`
Method Resolution Order	✅ Supported	MRO with multiple inheritance	`differential_312_test.py`

Comprehensions¶

Feature	Status	Notes	Test File
List comprehension	✅ Supported	`[x for x in iter]`	`test_list_comprehension`
Dict comprehension	✅ Supported	`{k: v for k, v in iter}`	`test_dict_comprehension`
Set comprehension	✅ Supported	`{x for x in iter}`	`test_set_comprehension`
Generator expression	✅ Supported	`(x for x in iter)`	`test_generator_expression`
Nested comprehension	✅ Supported	Multiple `for` clauses	`test_nested_comprehension`
Comprehension with conditions	✅ Supported	`[x for x in iter if cond]`	`test_comprehension_conditions`
Scope isolation	✅ Supported	Variables don't leak	`differential_312_test.py`

Collections¶

Lists¶

Feature	Status	Notes	Test File
List literal	✅ Supported	`[1, 2, 3]`	`test_list_literal`
List indexing	✅ Supported	`lst[0]`	`test_list_indexing`
List slicing	✅ Supported	`lst[1:3]`	`test_list_slicing`
List methods	✅ Supported	`.append()`, `.extend()`, etc.	`test_list_methods`

Dictionaries¶

Feature	Status	Notes	Test File
Dict literal	✅ Supported	`{k: v}`	`test_dict_literal`
Dict indexing	✅ Supported	`d[key]`	`test_dict_indexing`
Dict unpacking	✅ Supported	`{d1, d2}`	`test_dict_unpacking`
Dict methods	✅ Supported	`.keys()`, `.values()`, etc.	`test_dict_methods`

Sets¶

Feature	Status	Notes	Test File
Set literal	✅ Supported	`{1, 2, 3}`	`test_set_literal`
Set operations	✅ Supported	Union, intersection, difference	`test_set_operations`
Set methods	✅ Supported	`.add()`, `.remove()`, etc.	`test_set_methods`

Tuples¶

Feature	Status	Notes	Test File
Tuple literal	✅ Supported	`(1, 2, 3)` or `1, 2, 3`	`test_tuple_literal`
Tuple unpacking	✅ Supported	`a, b = (1, 2)`	`test_tuple_unpacking`
Tuple indexing	✅ Supported	`tup[0]`	`test_tuple_indexing`

Imports¶

Feature	Status	Notes	Test File
`import module`	✅ Supported	Import module	`test_import_module`
`import ... as ...`	✅ Supported	Alias imports	`test_import_alias`
`from ... import ...`	✅ Supported	Import from module	`test_from_import`
`from ... import ... as ...`	✅ Supported	Alias for imported item	`test_from_import_alias`
`from ... import *`	✅ Supported	Wildcard import	`test_wildcard_import`
Relative imports	✅ Supported	`from . import`	`test_relative_import`
Package imports	✅ Supported	`import pkg.subpkg`	`test_package_import`

Advanced Features¶

Pattern Matching¶

Feature	Status	Notes	Test File
`match` statement (PEP 634)	✅ Supported	Pattern matching	`test_match_statement`
`case` clauses	✅ Supported	Case patterns	`test_case_patterns`
Default case	✅ Supported	`case _:`	`test_default_case`
Guard clauses	✅ Supported	`case x if cond:`	`test_guard_clauses`
OR patterns	✅ Supported	`case a \\| b:`	`test_or_patterns`
Capture patterns	✅ Supported	`case Point(x, y):`	`test_capture_patterns`
Sequence patterns	⚠️ Partial	Not comprehensive	`PENDING`
Mapping patterns	⚠️ Partial	Not comprehensive	`PENDING`

Async/Await¶

Feature	Status	Notes	Test File
`async def`	✅ Supported	Async function definition	`test_async_def`
`await`	✅ Supported	Await coroutine	`test_await`
`async for`	✅ Supported	Async iteration	`test_async_for`
`async with`	✅ Supported	Async context manager	`test_async_with`

Context Managers¶

Feature	Status	Notes	Test File
`with` statement	✅ Supported	Context manager	`test_with_statement`
Multiple context managers	✅ Supported	`with a, b:`	`test_multiple_context_managers`
`as` binding	✅ Supported	`with ... as var:`	`test_context_manager_as`

Assertions¶

Feature	Status	Notes	Test File
`assert` statement	✅ Supported	Assertion	`test_assert`
`assert` with message	✅ Supported	`assert x, "message"`	`test_assert_message`

Scope & Closures¶

Feature	Status	Notes	Test File
`global` declaration	✅ Supported	Access global variable	`test_global`
`nonlocal` declaration	✅ Supported	Access enclosing scope	`test_nonlocal`
Closure creation	✅ Supported	Nested function with captures	`test_closures`
Late binding	✅ Supported	Variable capture timing	`differential_312_test.py`

Python 3.12 Specific Features (PEPs)¶

PEP	Feature	Status	Notes
PEP 634	Structural Pattern Matching (`match/case`)	✅ Supported	Basic patterns working
PEP 646	Variadic Generics (`TypeVarTuple`)	⚠️ Not Planned	Type system feature
PEP 647	User-Defined Type Guards	⚠️ Not Planned	Type system feature
PEP 655	Marking Dataclass Fields as Required/Not Required	⚠️ Not Planned	Type system feature
PEP 661	Sentinel Values	⚠️ Not Planned	Design pattern
PEP 673	`Self` Type	⚠️ Not Planned	Type system feature
PEP 675	Arbitrary Precision Integers	✅ Supported	Python default behavior
PEP 680	Data Class Transforms	⚠️ Not Planned	Type system decorator
PEP 688	Make buffer protocol accessible	⚠️ Not Planned	C API feature
PEP 692	Type Parameter Syntax	❌ Not Supported	PEP 695 replacement
PEP 695	Type Parameter Syntax (Final)	❌ Not Supported	`type X = ...`, `def f[T](...):`
PEP 698	Override Decorator	❌ Not Supported	`@override`
PEP 701	F-string Syntax	✅ Supported	Full f-string support
PEP 709	Improved Error Locations in Tracebacks	✅ Supported	Error reporting

Known Gaps & Limitations¶

Not Implemented (Intentional)¶

Type System Features (PEP 695, 692, 673, etc.) - Out of scope for runtime
Buffer Protocol (PEP 688) - Low priority
Dataclass Transforms (PEP 680) - Type system
Override Decorator (PEP 698) - Type annotation feature

Partial Implementation¶

Pattern Matching - Basic patterns work; complex structural patterns limited
Async/Await - Core functionality working; advanced scenarios may need testing
Unicode Operators - Not all Unicode variants tested comprehensively

Areas Needing Expansion (v0.4.0 Focus)¶

Edge case syntax forms (deeply nested, complex combinations)
Negative test coverage (syntax errors, error messages)
AST normalization determinism across all 17 languages
Semantic parity with CPython 3.12 (exceptions, operators, scope)
Full stdlib parity (math, json, datetime, itertools, pathlib)
Real-world ecosystem compatibility

Test Coverage Goals (v0.4.0)¶

Category	Current	Target	Gap
Syntax Coverage	~80%	95%+	+15%
Semantic Coverage	~70%	95%+	+25%
Import/Stdlib	~60%	95%+	+35%
Ecosystem Compat	~40%	85%+	+45%
Multilingual (17 langs)	~50%	90%+	+40%

Verification Strategy¶

Phase 1 (Checklist): Document all features and map to tests Phase 2 (Testing): Implement comprehensive test coverage for gaps Phase 3 (Validation): Run full test suite, fix failures Phase 4 (Release): Document achievements, publish compatibility score