运算符和表达式

算术运算

python在这里直接支持了幂运算，c的话需要额外的头文件导入

此外，python也是支持取模%和取整运算的。

The / (division) and // (floor division) operators yield the quotient of their arguments. The numeric arguments are first converted to a common type. Division of integers yields a float, while floor division of integers results in an integer; the result is that of mathematical division with the ‘floor’ function applied to the result.