How to emulate 4-bit integer in Python 3? -

i'd emulate overflow behavior of unsigned 4-bit integers, this:

>>> x, y = int4(10), int4(9) >>> x + y int4(3) >>> x * y int4(10) 

inheritance of builtin int seems work. possible implement int4 class without overriding operator methods __add__?

no, subclassing int not automatically re-use type when applying arithmetic it:

>>> class int4(int): ...     def __new__(cls, i): ...         return super(int4, cls).__new__(cls, & 0xf) ...  >>> x, y = int4(10), int4(9) >>> x + y 19 >>> type(x + y) <type 'int'> 

you have override __add__, etc. methods cast int4() when this.

if ever want support type (e.g. not support converting other numeric types in process), can generate of these:

from functools import wraps  class int4(int):     def __new__(cls, i):         return super(int4, cls).__new__(cls, & 0xf)  def add_special_method(cls, name):     mname = '__{}__'.format(name)     @wraps(getattr(cls, mname))     def convert_to_cls(self, other):         bound_original = getattr(super(cls, self), mname)         return type(self)(bound_original(other))     setattr(cls, mname, convert_to_cls)  m in ('add', 'sub', 'mul', 'floordiv', 'mod', 'pow',           'lshift', 'rshift', 'and', 'xor', 'or'):     add_special_method(int4, m)     add_special_method(int4, 'r' + m)  # reverse operation 

this produces methods always return type of self arithmetic special methods; this'll allow further subclassing of int4 well.

demo:

>>> functools import wraps >>> class int4(int): ...     def __new__(cls, i): ...         return super(int4, cls).__new__(cls, & 0xf) ...  >>> def add_special_method(cls, name): ...     mname = '__{}__'.format(name) ...     @wraps(getattr(cls, mname)) ...     def convert_to_cls(self, other): ...         bound_original = getattr(super(cls, self), mname) ...         return type(self)(bound_original(other)) ...     setattr(cls, mname, convert_to_cls) ...  >>> m in ('add', 'sub', 'mul', 'floordiv', 'mod', 'pow', ...           'lshift', 'rshift', 'and', 'xor', 'or'): ...     add_special_method(int4, m) ...     add_special_method(int4, 'r' + m)  # reverse operation ...  >>> x, y = int4(10), int4(9) >>> x + y 3 >>> x * y 10