2.6 Arithmetic
If we are to think of Python as a super-calculator, we must do the basic
arithmetic operations. We write addition, negation, and subtraction in the usual ways with
“+”, “-”, and “-”, respectively.
m, n = 17, 6
m + n
23
-n
-6
n - m
-11
There is no multiplication sign “×” on a keyboard, so we use the asterisk “*”.
m * n
102
Floating-point numbers are contagious. Once you use a decimal point, the remaining
arithmetic operations usually proceed as float.
5 * 3.4
17.0
5 * 3.0
15.0
Python tries to do the right thing when comparing int and
float numbers. We test for equality using the “==” operator.
a = 100000000000000000000
b = 100000000000000000000.
a == b
True
Beware of round-off errors when working with float...