increase.py

def shift_array(array):
    array.insert(0,0)
    return array
def unshift_array(array):
    array.pop(0)
    return array

def increase(input):
    if input[0] == 9 :
        input = shift_array(input)

    idx = len(input)-1
    curry = 0
    while(idx > -1):
        if(idx == len(input)-1):
            input[idx] +=1
        input[idx] += curry
        if(input[idx] > 9):
            input[idx] = input[idx] % 10
            curry = 1
        else:
            curry = 0
        idx -= 1

    if input[0] == 0 :
        input = unshift_array(input)
    return input

input = [1,9,3,8]
print(increase(input))

input = [1]
print(increase(input))

input = [9]
print(increase(input))

input = [9,9,9]
print(increase(input))