matplotlib axis

http://matplotlib.org/api/_as_gen/matplotlib.pyplot.axis.html#matplotlib.pyplot.axis

axis('off') #关闭坐标轴
axis('equal') #changes limits of x or y axis so that equal increments of x and y have the same length; a circle is circular.
axis('scaled')
axis('tight')
axis('image')
axis('auto')
axis('normal')
axis('square') # 正方形