s5e4

import math
def my_log(n):
    ret_list = []
    for i in n:
        if i<=0:
            ret_list.append("None")
        else:
            ret_list.append(math.log(i))
    return(ret_list)
n = [1, 3, 2.5, -1, 9, 0, 2.71]
print(my_log(n))