How to cycle through an array

cycle_arr.py

import numpy as np

arr = ["A", "B", "C", "D"]

# I want this to cycle every 0.5s
# so I should see this list printed twice
# with each item printed 5 times
idx = 0
arr_len = len(arr)
t_len = 0.5

for t in np.arange(0, 4.0, 0.1):
    idx = int(np.floor(t % (t_len * arr_len) / t_len)) #  this line is the solution
    print(arr[idx])