title: Keyerror (key) from none (python)
body: <p>This is the code I have. I am learning python and this is one of the practice codes from the video. But I am getting an error that I am unable to understand</p>
  
  <pre><code>def bytespdate2num(fmt, encoding='utf-8'):
      strconverter = mdates.strpdate2num(fmt)
      def bytesconverter(b):
          s = b.decode(encoding)
          return strconverter(s)
      return bytesconverter
  
  
  def graph_data(stock):
  
  
      ax1 = plt.subplot2grid((1,1), (0,0))
  
      stock_price_url = 'http://chartapi.finance.yahoo.com/instrument/1.0/'+stock+'/chartdata;type=quote;range=10y/csv'
      source_code = urllib.request.urlopen(stock_price_url).read().decode()
      stock_data = []
      split_source = source_code.split('\n')
      for line in split_source:
          split_line = line.split(',')
          if len(split_line) == 6:
              if 'values' not in line and 'labels' not in line:
                  stock_data.append(line)
  
      date, closep, highp, lowp, openp, volume = np.loadtxt(stock_data,
                                                            delimiter=',',
                                                            unpack=True,
                                                            converters={0: bytespdate2num('%Y%m%d')})
  
      ax1.plot_date(date, closep,'-', label='Price')
      for label in ax1.xaxis.get_ticklabels():
          label.set_rotation(45)
      ax1.grid(True)#, color='g', linestyle='-', linewidth=5)
  
      plt.xlabel('Date')
      plt.ylabel('Price')
      plt.title('Interesting Graph\nCheck it out')
      plt.legend()
      plt.subplots_adjust(left=0.09, bottom=0.20, right=0.94, top=0.90, wspace=0.2, hspace=0)
      plt.show()
  
  
  graph_data('TSLA')
  </code></pre>
  
  <p>The error that I am getting is this:</p>
  
  <pre><code>Traceback (most recent call last):
    File "C:\Users\sponnag1\workspace\DataAnalysisWithPython\DataAnalysis.py", line 19, in &lt;module&gt;
      from spyder.utils.site.sitecustomize import matplotlib
    File "C:\Users\sponnag1\AppData\Local\Continuum\Anaconda3\lib\site-packages\spyder\utils\site\sitecustomize.py", line 225, in &lt;module&gt;
      if os.environ["QT_API"] == 'pyqt':
    File "C:\Users\sponnag1\AppData\Local\Continuum\Anaconda3\lib\os.py", line 725, in __getitem__
      raise KeyError(key) from None
  KeyError: 'QT_API'
  </code></pre>
  
  <p>How do I deal with this? </p>