python编译成功，但是执行没有结果咋整？

Question

random_walk.py

from random import choice

class RandomWalk():
    """ Generate random walk date class """
    
    def __init__(self,num_points=5000):
        """ initialise random walk date Class """
        
        self.num_points = num_points
        #all random walk start from ( 0 , 0 )
        self.x_values = [0]
        self.y_values = [0]
    
    def fill_walk(self):
        """ calculate all points contained in random walk """
       
        #~ Keep taking steps until the walk reaches the desired length.
        while len(self.x_values) < self.num_points:
            
            #~Decide which direction to go, and how far to go in that direction.
            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 = choice([0,1,2,3,4])
            y_step = y_direction * y_distance
            
            if x_step ==0 and y_step ==0:
                continue    
                
               
                next_x = self.x_values[-1]+x_step 
                next_y = self.y_values[-1]+y_step
                
                self.x_values.append(next_x)
                self.y_values.append(next_y)
      
  
            

rw_visual.py

import matplotlib.pyplot as plt
from random_walk import RandomWalk

while True:
    #create an instance of randomwalk and draw the points contained in randomwalk
    rw = RandomWalk(50000)
    rw.fill_walk()
    
    #set the size of window
    plt.figure(dpi=128, figsize=(8 ,6))
    #painting the point and appared it 
    point_numbers = list(range(rw.num_points))
    plt.scatter(rw.x_values, rw.y_values, c=point_numbers, 
                cmp=plt.cm.Blues, edgecolor = 'none' ,s=1)
      
    #start point and end point
    plt.scatter(0, 0,c='green', edgecolors='none', s=50)
    plt.scatter(rw.x_values[-1], rw.y_values[-1], c='red',
                edgecolor = 'none' ,s=50)
    
    #hide axss
    plt.axes().get_xaxis().set_visible(False)
    plt.axes().get_yaxis().set_visible(False)
    
    plt.show()
    keep_running = input("Make another walk(y/n):")
    if keep_running =='n':
        break
        

Answer 1

fill_walk都死循环了，当然看不到后面的输入提示了

当if条件，直接continue，添加元素的操作无法执行到
不满足if条件，添加元素的操作更无法执行到

self.x_values的长度就没变过。