+,
-, *, /, %, divmod(), pow(),
<<, >>, &, ^, |).
-, +,
abs() and ~).
__len__.
Note that this method is not called to coerce the arguments to +
and *, because these are also used to implement sequence
concatenation and repetition, respectively. Also note that, for the
same reason, in n*x, where n is a built-in number and
x is an instance, a call to x.__mul__(n) is made.
int(), long()
and float(). Should return a value of the appropriate type.
oct() and
hex(). Should return a string value.