Can anyone explain this output?

Question

print(-9%7)=5
print(-5%2)=1

But how can you explain this.

Answer 1

It depends on the division operator. Quotient q and remainder r relate through the equation : n = q*m + r

Python uses floor division (rounds towards minus infinity). Thus -9 // 7 is -2 and not -1 as is the case for division that round towards zero (for instance C/C++).

So, the remainder is:

r = -9 - 7*(-9//7) = -9 - 7*(-2) = -9 - (-14) = 5

In addition, you may find this article helpful:
https://en.wikipedia.org/wiki/Modulo_operation#Remainder_calculation_for_the_modulo_operation