TypeError: unsupported operand type(s) for +: 'int' and 'list'

请问这个错误如何解决，谢谢

from random import choice

class Randomwalk:
    def __init__(self, number_point=5000):
        self.number_point = number_point

        self.x_value = [0]
        self.y_value = [0]

    def fill_walk(self):
        while len(self.x_value) < self.number_point:
            x_direction = [1, -1]

            x_distance = choice([1, 2, 3, 4, 0])
            x_step = x_direction * x_distance

            y_direction = choice([1, -1])
            y_distance = choice([0, 1, 2, 3, 4])
            y_step = y_distance * y_direction

            if x_step == 0 and y_step == 0:
                continue
            x = self.x_value[-1] + x_step
            y = self.y_value[-1] + y_step
            self.y_value.append(y)
            self.x_value.append(x)