title: Why the Y axis scale is invisible and doesn't match with the actual value when using python matplotlib to draw graph?
body: <pre><code>#-*-coding:utf-8 -*-
  
  import csv
  import time
  import numpy as np
  import matplotlib.pyplot as plt
  
  Time=[]
  Temperature=[]
  
  plt.figure()
  
  with open('Temperature.csv', 'r') as csvfile:
      plots=csv.reader(csvfile, delimiter=',')
      header_row = next(plots)
      for column in plots:
          Time.append(time.strftime(column[0]))
          Temperature.append(column[1])
  
  ax = plt.gca()
  ax.set_ylim(0, 100)
  ax.set_yticks(np.arange(0, 100, 20))
  
  plt.plot(Time, Temperature, linewidth=5)
  plt.show()
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/ZlwyM.jpg" rel="nofollow noreferrer">enter image description here</a></p>
  
  <p>As title, the Y scale isn't visible and the graph value which is 28 actually is set as zero on the axis. So there is some issue for code?</p>