Python Program to get indices of sign change in a list

When it is required to get indices of sign change in a list, a simple iteration along with ‘append’ method can be used.

Example

Below is a demonstration of the same

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)

Output

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

Explanation

• A list is defined and is displayed on the console.

• An empty list is defined.

• The original list is iterated over, and conditions are set to check if the values at specific indices are less than or greater than 0.

• Depending on this, the index is appended to the empty list.

• This is displayed as the output on the console.