python报错unsupported operand type for+int and list

求问python使用matplotlib时遇到的问题

from random import choice



class RandomWalk:
	"""一个随机生成漫步数据的类"""
	def __init__(self, num_points=5000):
		"""初始化要漫步的属性"""
		self.num_points = num_points

		#所有随机漫步都始于(0,0)
		self.x_values = [0]
		self.y_values = [0]

	def fill_walk(self):
		"""计算随机漫步包含的所有点"""

		#不断漫步直到列表达到指定的长度
		while len(self.x_values) < self.num_points:

			#决定前进方向以及沿着这个方向前进的距离
			x_direction = choice([1, -1])

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

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

			#拒绝原地踏步
			if x_step == 0 and y_step == 0:
				continue

			#计算下一个点的x和y值
			x = self.x_values[-1] + x_step
			y = self.y_values[-1] + y_step

			self.x_values.append(x)
			self.y_value.append(y)

 调用上图代码

import matplotlib.pyplot as plt

from aaaaaa import RandomWalk

rw = RandomWalk()
rw.fill_walk()

plt.style.use('classic')
fig, ax = plt.subplots()
ax.scatter(rw.x_values, rw.y_values, s=15)

plt.show()

运行出现Traceback (most recent call last):
  File "C:\Users\86199\Desktop\rw_visual.py", line 6, in <module>
    rw.fill_walk()
  File "C:\Users\86199\Desktop\aaaaaa.py", line 37, in fill_walk
    y = self.y_values[-1] + y_step
TypeError: unsupported operand type(s) for +: 'int' and 'list'

错在这行，y_distance = ([0, 1, 2, 3, 4])，这个是一个列表，应该是y_distance = choice([0, 1, 2, 3, 4])