why does python floor division operator behaves like this?

Question

why does python floor division operator behaves like this?
I came across this code snippet and result was quite surprising.

a = 1 // 10 

b = -1 // 10

print a,b

a= 0

b=-1

printing output obtained results are

a=0

and

b= -1

.

why does

a=0

and

b= -1

?

//

does floor division, so it's always rounding down?

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Answer 1

// in Python is a "floor division" operator. That means that the result of such division is the floor of the result of regular division (performed with / operator).

The floor of the given number is the biggest integer smaller than the this number. For example

7 / 2 = 3.5 so 7 // 2 = floor of 3.5 = 3.

For negative numbers it is less intuitive: -7 / 2 = -3.5, so -7 // 2 = floor of -3.5 = -4. Similarly -1 // 10 = floor of -0.1 = -1.

// is defined to do the same thing as math.floor(): return the largest integer value less than or equal to the floating-point result. Zero is not less than or equal to -0.1.

why does python floor division operator behaves like this?

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