如何在matplotlib RectangleSelector回调中获取ax绘图ID？

要在回调函数中获取当前操作对应的子图（Axes）或其索引，核心思路是将子图的索引或对象传递给回调函数。以下是几种可行的实现方式：

方法1：使用Lambda表达式绑定参数 #

修改回调函数，让它接受额外的idx（子图索引）和ax（Axes对象）参数，然后在创建RectangleSelector时通过lambda将当前迭代的参数传递进去（注意用默认参数固定值，避免循环变量引用问题）：

from matplotlib.widgets import RectangleSelector
import numpy as np
import matplotlib.pyplot as plt

def select_callback(eclick, erelease, idx=None, ax=None):
    x1, y1 = eclick.xdata, eclick.ydata
    x2, y2 = erelease.xdata, erelease.ydata
    # 输出当前操作的子图信息
    print(f"当前操作的子图索引: {idx}")
    print(f"对应的Axes对象: {ax}")
    # 这里可以添加基于ax或idx的业务逻辑

fig = plt.figure(constrained_layout=True)
axs = fig.subplots(4)

x = np.linspace(0, 10, 1000)

selectors = []
for idx,ax in enumerate(axs):
    ax.plot(x, np.sin(2*np.pi*x))
    selectors.append(RectangleSelector(
        ax, 
        # 用lambda传递idx和ax，通过默认参数固定当前迭代的值
        lambda eclick, erelease, idx=idx, ax=ax: select_callback(eclick, erelease, idx=idx, ax=ax),
        useblit=True,
        button=[1, 3],
        minspanx=5, minspany=5,
        spancoords='pixels',
        interactive=True))

plt.show()

方法2：使用functools.partial绑定参数 #

通过functools.partial可以更清晰地将参数绑定到回调函数上，避免lambda的写法：

from matplotlib.widgets import RectangleSelector
import numpy as np
import matplotlib.pyplot as plt
from functools import partial

def select_callback(idx, ax, eclick, erelease):
    x1, y1 = eclick.xdata, eclick.ydata
    x2, y2 = erelease.xdata, erelease.ydata
    print(f"当前操作的子图索引: {idx}")
    print(f"对应的Axes对象: {ax}")

fig = plt.figure(constrained_layout=True)
axs = fig.subplots(4)

x = np.linspace(0, 10, 1000)

selectors = []
for idx,ax in enumerate(axs):
    ax.plot(x, np.sin(2*np.pi*x))
    # 使用partial将idx和ax绑定到回调函数的前两个参数
    bound_callback = partial(select_callback, idx, ax)
    selectors.append(RectangleSelector(
        ax, 
        bound_callback,
        useblit=True,
        button=[1, 3],
        minspanx=5, minspany=5,
        spancoords='pixels',
        interactive=True))

plt.show()

方法3：使用闭包定义回调函数 #

在循环内部定义回调函数，利用闭包捕获当前迭代的idx和ax：

from matplotlib.widgets import RectangleSelector
import numpy as np
import matplotlib.pyplot as plt

fig = plt.figure(constrained_layout=True)
axs = fig.subplots(4)

x = np.linspace(0, 10, 1000)

selectors = []
for idx,ax in enumerate(axs):
    ax.plot(x, np.sin(2*np.pi*x))
    # 内部回调函数捕获当前循环的idx和ax
    def select_callback(eclick, erelease):
        x1, y1 = eclick.xdata, eclick.ydata
        x2, y2 = erelease.xdata, erelease.ydata
        print(f"当前操作的子图索引: {idx}")
        print(f"对应的Axes对象: {ax}")
    selectors.append(RectangleSelector(
        ax, 
        select_callback,
        useblit=True,
        button=[1, 3],
        minspanx=5, minspany=5,
        spancoords='pixels',
        interactive=True))

plt.show()

以上三种方法都能实现需求，你可以根据自己的代码风格选择合适的方式。

内容的提问来源于stack exchange，提问作者joenpc npcsolution