python - 在多个 matplotlib.pyplot 子图上创建图例单击事件

Question

我有几个 matplolib.pyplot 图形。每个都有一个图例，我想要的是单击图例上的线隐藏图中的线。点击事件处理在这里找到:https://matplotlib.org/examples/event_handling/legend_picking.html

当只有一个图形时，此方法效果很好，但当有多个图形时，它仅适用于最后一个图形。当我单击另一个人物的图例时，我没有收到任何异常或警告，但什么也没有发生。

以下是解决此问题的示例代码:

import matplotlib.pyplot as plt
import numpy as np

a = np.arange(0,10,1)
    b = np.arange(0,20,2)
    c = np.arange(0,5,.5)
    d = np.arange(-1,9,1)

    lined = {}

    for var1, var2 in [(a,b), (c,d)]:
        fig, ax = plt.subplots()
        line1, = ax.plot(var1, label="l1")
        line2, = ax.plot(var2, label="l2")
        leg = fig.legend([line1, line2], ["l1", "l2"])
        legl1, legl2 = leg.get_lines()
        legl1.set_picker(5)
        lined[legl1] = line1
        legl2.set_picker(5)
        lined[legl2] = line2

        def onpick(event, figu):
            legl = event.artist
            origl = lined[legl]
            vis = not origl.get_visible()
            origl.set_visible(vis)
            if vis:
                legl.set_alpha(1.0)
            else:
                legl.set_alpha(0.2)
            figu.canvas.draw()

        fig.canvas.mpl_connect('pick_event', lambda ev: onpick(ev, fig))
    plt.show()

如何使点击事件也适用于第一个图形？

Answer 1

原因由 https://docs.python-guide.org/writing/gotchas/#late-binding-closures 给出。我必须承认我自己并不完全理解它，但它给出了解决它的技巧:使用默认参数。

import matplotlib.pyplot as plt
import numpy as np

a = np.arange(0,10,1)
b = np.arange(0,20,2)
c = np.arange(0,5,.5)
d = np.arange(-1,9,1)

lined = {}

for var1, var2 in [(a,b), (c,d)]:
    fig, ax = plt.subplots()
    line1, = ax.plot(var1, label="l1")
    line2, = ax.plot(var2, label="l2")
    leg = fig.legend([line1, line2], ["l1", "l2"])
    legl1, legl2 = leg.get_lines()
    legl1.set_picker(5)
    lined[legl1] = line1
    legl2.set_picker(5)
    lined[legl2] = line2

    def onpick(event, figu=fig):
        legl = event.artist
        origl = lined[legl]
        vis = not origl.get_visible()
        origl.set_visible(vis)
        if vis:
            legl.set_alpha(1.0)
        else:
            legl.set_alpha(0.2)
        figu.canvas.draw()

    fig.canvas.mpl_connect('pick_event', onpick)  # no need for a lambda
plt.show()

如前所述，该解决方案有点hacky。比较看似相同的内容

# works
    def onpick(event, figu=fig):
        (...)
        figu.canvas.draw()  # using a default arg equal to fig
    fig.canvas.mpl_connect('pick_event', onpick)

对比

# fails as described
    def onpick(event):
        (...)
        fig.canvas.draw()  # using fig from main loop directly
    fig.canvas.mpl_connect('pick_event', onpick)