code: def plot_one_month(x, y, xlabel=None, ylabel=None, title=None, ylim=None):
      
      plt.close("all")
      
      fig = plt.figure(figsize=(20, 10))
      ax = fig.add_subplot(111)
      ax.plot(x, y)
      
  
      days = DayLocator(range(365))
      daysFmt = DateFormatter("%Y-%m-%d")
      
      ax.xaxis.set_major_locator(days)
      ax.xaxis.set_major_formatter(daysFmt)
      
      ax.autoscale_view()
      ax.grid()
      plt.setp( ax.xaxis.get_majorticklabels(), rotation=90 )
      
      if xlabel:
          plt.xlabel(xlabel)
      else:
          plt.xlabel("Time")
          
      if ylabel:
          plt.ylabel(ylabel)
      else:
          plt.ylabel("Value")
      
      if title:
          plt.title(title)
      else:
          plt.title("%s to %s" % (str(x[0]), str(x[-1]) ) )
  
      if ylim:
          plt.ylim(ylim)
      else:
          plt.ylim([min(y) - (max(y) - min(y) ) * 0.05, 
                    max(y) + (max(y) - min(y) ) * 0.05])
      
      return plt, ax
docs: 时间跨度为一月。
      
      major tick = every days