matplotlib中,如何在坐标系中画一个矩形，matplotlib坐标系,import matpl

matplotlib中,如何在坐标系中画一个矩形，matplotlib坐标系,import matpl

import matplotlib.pyplot as plt from matplotlib.patches import Rectangle  class Annotate(object):    def __init__(self):        self.ax = plt.gca()        self.rect = Rectangle((0,0), 1, 1)        self.x0 = None                 self.y0 = None                 self.x1 = None                 self.y1 = None                 self.ax.add_patch(self.rect)        self.ax.figure.canvas.mpl_connect('button_press_event', self.on_press)        self.ax.figure.canvas.mpl_connect('button_release_event', self.on_release)    def on_press(self, event):        print 'press'                 self.x0 = event.xdata                 self.y0 = event.ydata          def on_release(self, event):                 print 'release'                 self.x1 = event.xdata                 self.y1 = event.ydata                 self.rect.set_width(self.x1 - self.x0)        self.rect.set_height(self.y1 - self.y0)                 self.rect.set_xy((self.x0, self.y0))                 self.ax.figure.canvas.draw()  a = Annotate() plt.show()