1，位置。loc=‘upper right’ 或者loc=1这样设置。还有如下备选项。
'best': 0, # only implemented for axes legends 'upper right': 1, 'upper left': 2, 'lower left': 3, 'lower right': 4, 'right': 5, 'center left': 6, 'center right': 7, 'lower center': 8, 'upper center': 9, 'center': 10,2，利用bbox_to_anchor这个参数，可以把图例放在图外面。见这里
3，设置透明的图例，见这里
4，设置图例字体大小，fontsize参数 : int or float or {‘xx-small’, ‘x-small’, ‘small’, ‘medium’, ‘large’, ‘x-large’, ‘xx-large’}，只有这7种调节值。 也可以利用prop参数：先定义font1 = {'size': 15} 。然后令参数prop=font1，这样可以随意调整字体大小。
下面这些是他的所有参数。
def __init__(self, parent, handles, labels, loc=None, numpoints=None, # the number of points in the legend line markerscale=None, # the relative size of legend markers # vs. original markerfirst=True, # controls ordering (left-to-right) of # legend marker and label scatterpoints=None, # number of scatter points scatteryoffsets=None, prop=None, # properties for the legend texts fontsize=None, # keyword to set font size directly # spacing & pad defined as a fraction of the font-size borderpad=None, # the whitespace inside the legend border labelspacing=None, # the vertical space between the legend # entries handlelength=None, # the length of the legend handles handleheight=None, # the height of the legend handles handletextpad=None, # the pad between the legend handle # and text borderaxespad=None, # the pad between the axes and legend # border columnspacing=None, # spacing between columns ncol=1, # number of columns mode=None, # mode for horizontal distribution of columns. # None, "expand" fancybox=None, # True use a fancy box, false use a rounded # box, none use rc shadow=None, title=None, # set a title for the legend framealpha=None, # set frame alpha edgecolor=None, # frame patch edgecolor facecolor=None, # frame patch facecolor bbox_to_anchor=None, # bbox that the legend will be anchored. bbox_transform=None, # transform for the bbox frameon=None, # draw frame handler_map=None, ):