Will return List of digits of a non - negative number incremented by 1

PLUS1.py

def plusOne(A):
    """
    :param A: List containing digits of a non - negative number
    :return: List containing digits after addition of 1 
    """"
        length = len(A)
        number = 0
        i = length - 1
        while A[i] + 1 > 9 and i >= 0:
            A[i] = 0
            i = i - 1
        if i < 0 :
            i = i + 1
            A.insert(0, 0)
        A[i] = A[i] + 1
        number = 0
        res = []
        for i in range(len(A)) :
            number += A[i]
            if number != 0 :
                res.append(A[i])
        return res
print(plusOne([0, 1, 2, 3])) # Will Return [1, 2, 4]
print(plusOne([9, 9, 9, 9])) # Will Return [1, 0, 0, 0]
print(plusOne([0, 0, 0])) # Will Return [1]