Ceil and floor equivalent in Python 3 without Math module?

Question

I need to ceil and floor 3/2 result (1.5) without using import math.

math.floor(3/2) => 3//2 math.ceil(3/2) => ?

OK, here is the problem: to sum all numbers 15 + 45 + 15 + 45 + 15 ... with N items.

sum = (n//2) * 5 + int(n/2) * 15

Answer 1

>>> 3/2 1.5 >>> 3//2 # floor 1 >>> -(-3//2) # ceil 2 

Answer 2

Try

def ceil(n):     return int(-1 * n // 1 * -1)  def floor(n):     return int(n // 1) 

I used int() to make the values integer. As ceiling and floor are a type of rounding, I thought integer is the appropriate type to return.

The integer division //, goes to the next whole number to the left on the number line. Therefore by using -1, I switch the direction around to get the ceiling, then use another * -1 to return to the original sign. The math is done from left to right.