python - Matplotlib图例使图像太大

诀窍是仅将标签设置一次。您可以为每个标签添加一个变量，并在使用None后将其替换为变量。注意，使用axvline背景绘制存在以下问题：线宽是在像素空间中测量的，因此相邻的线会重叠或之间有小的空白。更好地使用axvspan。为了避免左右两边的空白，您可以显式设置x限制。

使用循环可以稍微简化代码。

更新的代码：

• 将连续的跨度分组以进行绘制
• 预先计算Alpha的效果，因此无需透明度即可绘制背景

from matplotlib import pyplot as plt
from matplotlib import colors as mcolors
import numpy as np
import pandas as pd
import itertools

fig, ax = plt.subplots()

# create some random data
x = np.arange(100)
y = np.sinh(x/20)
indicators = [-1, 0, 1]
node = 0
data = [np.random.choice(indicators, len(x), p=[10/16,1/16,5/16])]

labels = ["OUT", "RZ0", "RZ1"]
colors = ['lime', 'purple', 'gold']

alpha = 0.4
# precalculate the effect of alpha so the colors can be applied with alpha=1
colors = [[1 + (x - 1) * alpha for x in mcolors.to_rgb(c)] for c in colors]

m = 0
for val, group in itertools.groupby(data[node]):
    width = len(list(group))
    ind = indicators.index(val)
    ax.axvspan(m, m + width, color=colors[ind], linewidth=0, alpha=1, label=labels[ind])
    labels[ind] = None  # reset the label to make sure it is only used once
    m += width

ax.plot(x, y, 'b+')
ax.set_xlim(0, len(data[node]))
ax.legend(framealpha=1) # to make the legend background opaque
plt.show()