python画图的图例legend设置。
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,
):