>>>> float('½')
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> ValueError: could not convert string to float: �
> 
>>>> float('42½')
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> ValueError

Note that fractional Unicode code points are not supported
by the encoding function.  Neither are code points which do
not evaluate to 0-9, e.g. ones that represent numbers
larger than 9.