Python / vs //: Floor Division Explained
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Python has two division operators: / performs regular division, while // performs floor division.
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Integers, Floats, and Division
Numbers without a decimal point are integers — whole numbers, positive or negative. Numbers with a decimal point are floats.
my_int = 5
my_float = 5.5
Basic arithmetic works the way you'd expect:
2 + 1 # 3 (addition)
2 - 1 # 1 (subtraction)
2 * 2 # 4 (multiplication)
3 / 2 # 1.5 (division)
One gotcha: division with / always returns a float, even if both operands are integers. 6 / 3 gives you 2.0, not 2.
What Is Floor Division in Python?
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Floor division is like normal division except the result is rounded down to the nearest integer. Use the // operator:
7 // 3 # 2 (rounded down from 2.333)
-7 // 3 # -3 (rounded down from -2.333)
Note that "rounded down" means toward negative infinity, not toward zero. That's why -7 // 3 is -3, not -2.
Use / when you need the ordinary quotient. Use // when you deliberately need the quotient rounded down.
Frequently Asked Questions
What is the difference between / and // in Python?
The / operator performs regular division and always returns a float. The // operator performs floor division, rounding the quotient down to the nearest integer.
Why does -7 // 3 equal -3 in Python?
Floor division rounds toward negative infinity, not toward zero. The quotient is about -2.333, so flooring it produces -3.
Does regular division always return a float in Python?
Yes. The / operator returns a float even when both operands are integers and divide evenly.
Does floor division round toward zero?
No. It rounds down toward negative infinity, which is why -7 // 3 equals -3 rather than -2.
