Nsryjdtyk

Please see the following code:

class PickCursor(object):

    def __init__(self, collection, alpha_other=0.3, tolerance=5):

        self.collection = collection

        self.alpha_other = alpha_other



        self.pts= collection.get_offsets()

        self.num_pts = len(self.pts)

        # Need to set a tolerance to make it take effect

        self.collection.set_picker(tolerance)



        # Ensure that we have separate colors for each object

        self.fc = collection.get_facecolors()

        if len(self.fc) == 0:

            raise ValueError('Collection must have a facecolor')

        elif len(self.fc) == 1:

            self.fc = np.tile(self.fc, (self.num_pts, 1))

        # self.fc is a 2d array every row follows [r, g, b, a]



        self.ind = None

        self.point_selected = None

        self.canvas = ax.figure.canvas

        self.canvas.mpl_connect('pick_event', self.onselect)



    def onselect(self, event):

        self.ind = event.ind[0]

        self.point_selected = self.pts[self.ind]

        # Change alpha of other points

        self.fc[:, -1] = self.alpha_other

        self.fc[self.ind, -1] = 1

        self.collection.set_facecolors(self.fc)

        self.canvas.draw_idle()



fig, ax = plt.subplots(1, 1, figsize=(8, 8))

x = np.arange(0, 10)

y = np.arange(0, 10)

scat = ax.scatter(x, y, s=15)

PickCursor(scat)

The above code works! Basically, it will make points unselected transparent. However, if I wrap the code into a function like this:

def func():

    fig, ax = plt.subplots(1, 1, figsize=(8, 8))

    x = np.arange(0, 10)

    y = np.arange(0, 10)

    scat = ax.scatter(x, y, s=15)

    PickCursor(scat)



func() ## this line does not work!!!

Anyone please shred some light on this? Thanks!

Your class is being garbage collected because you don't retain a reference to it.

def func():

    # ...

    return PickCursor(scat)



pc = func()