A minimal integer ID type that intentionally doesn't support mathematical operations

integer_id.py

# A minimalist integer ID type that intentionally doesn't support mathematical
# operations. Subclass it to make e.g. UserID type, FileDescriptor type

class ID(object):
    __slots__ = ('_v',)
    def __init__(self, v):
        if not isinstance(v, int):
            raise TypeError('int required, got: %s"' % type(v))
        if v < 0:
            raise ValueError('cannot be negative', v)
        super(ID, self).__setattr__('_v', v)
    def __setattr__(self, name, v): raise AttributeError('Immutable')
    def __eq__(self, x): return isinstance(x, type(self)) and self._v == x._v
    def __hash__(self): return hash((self._v,))
    def __int__(self): return self._v
    def __str__(self): return str(self._v)
    def __repr__(self): return '%s(%d)' % (type(self).__name__, self._v)