算数运算符
二元运算符：
+(加)-(减)*(乘)/(除)^(幂)%(取余)一元运算符：
-(负)
a = 10
b = 7
print(a + b) --> 17
print(a - b) --> 3
print(a * b) --> 70
print(a / b) --> 1.4285714285714
print(a ^ b) --> 10000000
print(a % b) --> 3
print(-a) --> -10