>>> import matplotlib.pyplot as plt

>>> import numpy as np

>>> x = np.linspace(-3, 3, 50)

>>> y1 = 2*x + 1

>>> y2 = x**2

>>> plt.figure()

<Figure size 640x480 with 0 Axes>

>>> plt.xlim((-1, 2))

(-1, 2)

>>> plt.ylim((-2, 3))

(-2, 3)

>>> new_sticks = np.linspace(-1, 2, 5)

>>> plt.xticks(new_sticks)

([<matplotlib.axis.XTick object at 0x000001C38FA6F198>, <matplotlib.axis.XTick object at 0x000001C38F57F748>, <matplotlib.axis.XTick object at 0x000001C38F57F0F0>, <matplotlib.axis.XTick object at 0x000001C38F516D30>, <matplotlib.axis.XTick object at 0x000001C38F59D908>], <a list of 5 Text xticklabel objects>)

>>> plt.yticks([-2, -1.8, -1, 1.22, 3],

...            [r'$really\ bad$', r'$bad$', r'$normal$', r'$good$', r'$really\ good$'])

([<matplotlib.axis.YTick object at 0x000001C38F50E668>, <matplotlib.axis.YTick object at 0x000001C38F2DD828>, <matplotlib.axis.YTick object at 0x000001C38F57FBE0>, <matplotlib.axis.YTick object at 0x000001C38F59D6A0>, <matplotlib.axis.YTick object at 0x000001C38F59D438>], <a list of 5 Text yticklabel objects>)

>>> l1, = plt.plot(x, y1, label='linear line')

>>> l2, = plt.plot(x, y2, color='red', linewidth=1.0, linestyle='--', label='square line')

#legend将要显示的信息来自于上面代码中的 label. 所以我们只需要简单写下一下代码, plt 就能自动的为我们添加图例

#参数 loc='upper right' 表示图例将添加在图中的右上角.

>>> plt.legend(loc='upper right')

<matplotlib.legend.Legend object at 0x000001C38B7D8780>

>>> plt.show()

>>> plt.legend(handles=[l1, l2], labels=['up', 'down'],  loc='best')

<matplotlib.legend.Legend object at 0x000001C38FA44630>

>>> plt.show()

 'best' : 0,

 '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,