modulus of negative numbers in Python [duplicate]

Question

23 % -5 = -2
23 % 5 = 3

Can someone explain to me how I can understand this because I have an exam tomorrow. I want to say its because -5 * -5 =25 then 25 -2 = 23 which is how they get the 23. Is this correct?

Answer 1

In Python, the sign of the remainder is the same as the sign of the denominator (which differs from languages like C, where it is the same as the sign of the numerator).

Mathematically, you are always guaranteed that if a, b = divmod(n, d), then a*d + b == n.

Note that 23//5 == 4 and 23//-5 == -5 (Python always does floor division). Thus, we have 4*5 + 3 == 23 and -5*-5 - 2 == 23, as you have said.