importmatplotlib.pyplotaspltimportnumpyasnpfrommatplotlib.backend_basesimportMouseButtonfrommatplotlib.patchesimportPathPatchfrommatplotlib.pathimportPathfig,ax=plt.subplots()pathdata=[(Path.MOVETO,(1.58,-2.57)),(Path.CURVE4,(0.35,-1.1)),(Path.CURVE4,(-1.75,2.0)),(Path.CURVE4,(0.375,2.0)),(Path.LINETO,(0.85,1.15)),(Path.CURVE4,(2.2,3.2)),(Path.CURVE4,(3,0.05)),(Path.CURVE4,(2.0,-0.5)),(Path.CLOSEPOLY,(1.58,-2.57)),]codes,verts=zip(*pathdata)path=Path(verts,codes)patch=PathPatch(path,facecolor='green',edgecolor='yellow',alpha=0.5)ax.add_patch(patch)classPathInteractor:"""    A path editor.    Press 't' to toggle vertex markers on and off.  When vertex markers are on,    they can be dragged with the mouse.    """showverts=Trueepsilon=5# max pixel distance to count as a vertex hitdef__init__(self,pathpatch):self.ax=pathpatch.axescanvas=self.ax.figure.canvasself.pathpatch=pathpatchself.pathpatch.set_animated(True)x,y=zip(*self.pathpatch.get_path().vertices)self.line,=ax.plot(x,y,marker='o',markerfacecolor='r',animated=True)self._ind=None# the active vertexcanvas.mpl_connect('draw_event',self.on_draw)canvas.mpl_connect('button_press_event',self.on_button_press)canvas.mpl_connect('key_press_event',self.on_key_press)canvas.mpl_connect('button_release_event',self.on_button_release)canvas.mpl_connect('motion_notify_event',self.on_mouse_move)self.canvas=canvasdefget_ind_under_point(self,event):"""        Return the index of the point closest to the event position or *None*        if no point is within ``self.epsilon`` to the event position.        """xy=self.pathpatch.get_path().verticesxyt=self.pathpatch.get_transform().transform(xy)# to display coordsxt,yt=xyt[:,0],xyt[:,1]d=np.sqrt((xt-event.x)**2+(yt-event.y)**2)ind=d.argmin()returnindifd[ind]<self.epsilonelseNonedefon_draw(self,event):"""Callback for draws."""self.background=self.canvas.copy_from_bbox(self.ax.bbox)self.ax.draw_artist(self.pathpatch)self.ax.draw_artist(self.line)defon_button_press(self,event):"""Callback for mouse button presses."""if(event.inaxesisNoneorevent.button!=MouseButton.LEFTornotself.showverts):returnself._ind=self.get_ind_under_point(event)defon_button_release(self,event):"""Callback for mouse button releases."""if(event.button!=MouseButton.LEFTornotself.showverts):returnself._ind=Nonedefon_key_press(self,event):"""Callback for key presses."""ifnotevent.inaxes:returnifevent.key=='t':self.showverts=notself.showvertsself.line.set_visible(self.showverts)ifnotself.showverts:self._ind=Noneself.canvas.draw()defon_mouse_move(self,event):"""Callback for mouse movements."""if(self._indisNoneorevent.inaxesisNoneorevent.button!=MouseButton.LEFTornotself.showverts):returnvertices=self.pathpatch.get_path().verticesvertices[self._ind]=event.xdata,event.ydataself.line.set_data(zip(*vertices))self.canvas.restore_region(self.background)self.ax.draw_artist(self.pathpatch)self.ax.draw_artist(self.line)self.canvas.blit(self.ax.bbox)interactor=PathInteractor(patch)ax.set_title('drag vertices to update path')ax.set_xlim(-3,4)ax.set_ylim(-3,4)plt.show()

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