import sys
if sys.version_info[0:2] < (3, 5):
raise ValueError('Python >=3.5 is required!')
# Example usage:
# from auto_assign import *
# class Xyz:
# @auto_assign
# def __init__(self, x: AutoAssign[int]) -> None:
# pass
# xyz = Xyz(1)
# print(xyz.x) # 1
# (See the description for more details...)
from typing import Any, Callable, TypeVar, Union, cast
import inspect
class _AutoAssignMagic: pass
_T = TypeVar('_T')
AutoAssign = Union[_AutoAssignMagic, _T]
_F = TypeVar('_F', bound=Callable[..., Any])
def auto_assign(func: _F) -> _F:
def _wrap(*args, **kw):
if not args:
# Where is self? Let the function figure it out!
func(*args, **kw)
self = args[0]
sig = inspect.signature(func)
auto_args = set()
for param in sig.parameters.values():
# XXX: Hacky way of checking for AutoAssign.
if hasattr(param.annotation, '__origin__') and \
param.annotation.__origin__ is AutoAssign:
auto_args.add(param.name)
try:
bound = sig.bind(*args, **kw)
except TypeError:
# Just let it propagate down to the function itself.
pass
else:
bound.apply_defaults()
for auto_arg in auto_args:
setattr(self, auto_arg, bound.arguments[auto_arg])
func(*args, **kw)
return cast(F, _wrap)
