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  1. import functools
  2.  
  3.  
  4. def isdunder(x):
  5.     return isinstance(x, str) and x.startswith('__') and x.endswith('__')
  6.  
  7.  
  8. class DunderSet:
  9.     def __contains__(self, x):
  10.         return isdunder(x)
  11.  
  12.  
  13. def wrap_method(method, xtype, cast):
  14.  
  15.     @functools.wraps(method)
  16.     def retval(*args, **kwargs):
  17.         result = method(*args, **kwargs)
  18.         return cast(result) if type(result) == xtype else result
  19.  
  20.     return retval
  21.  
  22.  
  23. def wrap_getter(method, xtype, cast, exceptions):
  24.     @functools.wraps(method)
  25.     def retval(self, name, *args, **kwargs):
  26.         result = method(self, name, *args, **kwargs)
  27.         return result if name in exceptions else check_type(result, xtype, cast)
  28.  
  29.     return retval
  30.  
  31.  
  32. def check_type(value, xtype, cast):
  33.     if type(value) == xtype:
  34.         return cast(value)
  35.     if callable(value):
  36.         return wrap_method(value, xtype, cast)
  37.     return value
  38.  
  39.  
  40. class ClosedMeta(type):
  41.     def __new__(meta, name, bases, dct, **kwargs):
  42.         if 'exceptions' in kwargs:
  43.             exceptions = set(['__new__', '__init__', *map(str, kwargs.pop('exceptions'))])
  44.         else:
  45.             exceptions = DunderSet()
  46.         target = kwargs.pop('target', bases[0] if bases else object)
  47.  
  48.         cls = super().__new__(meta, name, bases, dct, **kwargs)
  49.  
  50.         for base in cls.__mro__:
  51.             for name, item in base.__dict__.items():
  52.                 if isdunder(name) and (base is cls or name not in dct) and callable(item):
  53.                     if name in ('__getattribute__', '__getattr__'):
  54.                         setattr(cls, name, wrap_getter(item, target, cls, exceptions))
  55.                     elif name not in exceptions:
  56.                         setattr(cls, name, wrap_method(item, target, cls))
  57.         return cls
  58.  
  59.     def __init__(cls, *args, **kwargs):
  60.         return super().__init__(*args)
  61.  
  62.  
  63. class MyInt(int):
  64.     def __contains__(self, x):
  65.         return x == self
  66.     def my_op(self, other):
  67.         return int(self * self // other)
  68.  
  69.  
  70. class ClosedInt(MyInt, metaclass=ClosedMeta, target=int,
  71.                 exceptions=['__index__', '__int__', '__trunc__']):
  72.     pass
  73.  
  74. class MyClass(ClosedInt, metaclass=type):
  75.     def __add__(self, other):
  76.         return 1
  77.  
  78. print(type(MyInt(1) + MyInt(2)))
  79. print(0 in MyInt(0), 1 in MyInt(0))
  80. print(type(MyInt(4).my_op(16)))
  81.  
  82. print(type(ClosedInt(1) + ClosedInt(2)))
  83. print(0 in ClosedInt(0), 1 in ClosedInt(0))
  84. print(type(ClosedInt(4).my_op(16)))
  85.  
  86. print(type(MyClass(1) + ClosedInt(2)))
Success #stdin #stdout 0.02s 27624KB
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stdin
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Standard input is empty
stdout
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<class 'int'>
True False
<class 'int'>
<class '__main__.ClosedInt'>
True False
<class '__main__.ClosedInt'>
<class 'int'>
https://ideone.com/iTBFW3
language:
Python 3 (python  3.9.5)
created:
5 years ago
visibility:
public

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