python - 代码是什么意思？ self.plusOne(数字[ :-1]) digits. 扩展([0])

Question

digits = self.plusOne(digits[:-1])
digits.extend([0])

完整代码:

def plusOne(self, digits):
    """
    :type digits: List[int]
    :rtype: List[int]
    """
    if len(digits) == 0:
        digits = [1]
    elif digits[-1] == 9:
        digits = self.plusOne(digits[:-1])
        digits.extend([0])
    else:
        digits[-1] += 1
    return digits

Answer 1

elif digits[-1] == 9:
    digits = self.plusOne(digits[:-1])
    digits.extend([0])

else if the last value in the list digits is a 9:
set digits = self.plusOne(all numbers in digits except the last)
add the number 0 to the list digits

例如:

digits = [9, 0, 9]
# digits = [9, 0, 9]
digits = self.plusOne([9, 0]) # this returns [9, 1]
# digits = [9, 1]
digits.extend([0])
# digits = [9, 1, 0]