On 1/6/2015 9:01 PM, Andrew Robinson wrote: [snip] There are very few (about 4) builtin classes that cannot be subclassed. bool is one of those few, float is not. Go ahead and subclass it. >>> class F(float): pass >>> F <class '__main__.F'> >>> F(2.3) + F(3.3) 5.6 -- Terry Jan Reedy