my_list = [71, 24, -34, -25, -76, 87, 29, -60, 70, 8]

print("The list is :")
print(my_list)
my_result = []
for index in range(0, len(my_list) - 1):

   if my_list[index] > 0 and my_list[index + 1] < 0 or my_list[index] < 0 and my_list[index + 1] < 0:

      my_result.append(index)

print("The result is :")
print(my_result)

The list is :
[71, 24, -34, -25, -76, 87, 29, -60, 70, 8]
The result is :
[1, 2, 3, 6]