def f():
    s = 0
    for i in range(N):
        s += i
    return s

N = 2
f()

1

N = 3
f()

3

from numba import njit
@njit()
def f():
    s = 0
    for i in range(N):
        s += i
    return s

N = 4
f()

6

N = 5
f()

6

f.recompile()

N = 5
f()

10