Replacing List Items

list_origin = [10, -15, 3, 8, 0, 9, -6, 13, -1, 5]
list_mask = []

for item in list_origin:
    if item > 0:
        list_mask.append(1)
    elif item < 0:
        list_mask.append(-1)
    else:
        list_mask.append(0)

print(list_origin)
print(list_mask)

# the old list
list_origin = [10, -15, 3, 8, 0, 9, -6, 13, -1, 5]

# the new list
list_mask = []

# enumeration of the elements of the old list
for item in list_origin:
    if item > 0:  # If the element is greater than 0,
        list_mask.append(1)  # 1 is added to the new list.
    elif item < 0:  # If the element is less than 0,
        list_mask.append(-1)  # -1 is added to the list.
    else:  # If the element is 0,
        list_mask.append(0)  # 0 is added to the list.

# output of source and derived lists
print(list_origin)
print(list_mask)

a = [10, -15, 3, 8, 0, 9, -6, 13, -1, 5]
print(a)

for i in range(len(a)):
    if a[i] > 0:
        a[i] = 1
    elif a[i] < 0:
        a[i] = -1

print(a)

a = [10, -15, 3, 8, 0, 9, -6, 13, -1, 5]
print(a)  # the list in its original form

# The i value changes from 0 to
# the index of the last item in the list,
# which is equal to the length of the list minus 1.
for i in range(len(a)):
    if a[i] > 0:  # If an element with index i is greater than 0,
        a[i] = 1  # then it is replaced by 1.
    elif a[i] < 0:  # If an element with index i is less than 0,
        a[i] = -1  # then it is replaced by -1.
    # In all other cases (the item is 0)
        # the element will remain as it is.

print(a)  # output of the changed list