1. matplotlib.legend.Legend是图例类，它的基类是matplotlib.artist.Artist。其构造函数为：  Legend(parent, handles, labels, loc=None, numpoints=None, markerscale =None, markerfirst=True, scatterpoints=None,  scatteryoffsets=None, prop=None, fontsize=None, borderpad =None, labelspacing=None, handlelength=None,  handleheight=None, handletextpad=None, borderaxespad =None, columnspacing=None, ncol=1, mode=None,  fancybox=None, shadow=None, title=None, framealpha =None, bbox_to_anchor=None, bbox_transform=None,  frameon=None, handler_map=None) 其关键字参数为：

• parent：持有该legend的artist
• loc:图例的位置。其值可以为字符串或者数字：
  • best或0：自动计算
  • upper right或1： 右上角
  • upper left或2：上角
  • lower left或3：下角
  • lower right或4：右下角
  • right或5：右边
  • center left或6：中间偏左
  • center right或7：中间偏右
  • lower center或8：中间底部
  • upper center或9：中间顶部
  • center或10：正中央
• handle：一个artist列表，添加这些artist到legend中
• lebels：一个字符串列表添加到legend中
• prop:字体属性
• fontsize: 字体大小（只有prop未设置时有效）
• markerscale: marker的缩放比例（相对于原始大小）
• markerfirst: 如果为True，则marker放在label左侧；否则marker放在label右侧
• numpoints: the number of points in the legend for line
• scatterpoints: the number of points in the legend for scatter plot
• scatteryoffsets: a list of offsets for scatter symbols in legend
• frameon: if True, draw a frame around the legend. If None, use rc
• fancybox: if True, draw a frame with a round fancybox. If None, use rc
• shadow: if True, draw a shadow behind legend
• framealpha: If not None, alpha channel for the frame.
• ncol: number of columns
• borderpad: the fractional whitespace inside the legend border
• labelspacing: the vertical space between the legend entries
• handlelength: the length of the legend handles
• handleheight: the height of the legend handles
• handletextpad: the pad between the legend handle and text
• borderaxespad: the pad between the axes and legend border
• columnspacing:the spacing between columns
• title: 图例的标题
• bbox_to_anchor: the bbox that the legend will be anchored.
• bbox_transform: the transform for the bbox. transAxes if Noneloc a location code
• 其他关键字参数用于设置属性

属性为：

• 继承自Artist基类的属性： .alpha、.animated、.axes、.clip_box、..clip_on、.clip_path、.contains、 .figure、.gid、.label、.picker、.transform、.url、.visible、.zorder