Integer and real results

When you do arithmetic in Python, the answer is not always a whole number. Every result has a type: either an integer (a whole number) or a real (a number with a decimal point, called a float in Python). Which one you get depends on the operator you use and on whether the values you start with are integers or reals.

Division always gives a real

The / operator always returns a real, even when the division works out exactly. 45 / 9 gives 5.0, not 5. Python writes the .0 to show the answer is a real, because a real is allowed to hold a fractional part even when this particular answer has not got one.

Integers in, integers out

If both values are positive integers, then +, -, *, //, % and ** all give an integer result. The table shows some expressions and the type of each result, so you can see how the type changes.

One real is enough

If either value in an arithmetic operation is a real, the result is a real too, whichever operator you use. So 25 + 1.5 gives 26.5, and 16 * 0.5 gives 8.0 — a whole-number value, but still a real because a real value was involved. When both values are positive integers, only / gives a real by itself; with the other operators you need at least one real value in the calculation before the answer becomes a real.