您面临的问题是，在绘制轴线之前，需要先绘制表格。如果您在ax.table(..)之后，axvline()和axhline()之前添加plt.draw()，它将工作。
x1c 0d1x的数据
完整更新代码…（只有一个额外的行：-））

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

df = pd.DataFrame(np.random.randn(8, 4), columns=["A", "B", "C", "D"])

fig, ax = plt.subplots()

tbl = ax.table(
    cellText=df.values,
    rowLabels=df.index,
    colLabels=df.columns,
    cellLoc="center",
    loc="center",
    fontsize=20,
    edges="open",
)

plt.draw()  ## The added line

ax.axvline(x=tbl[1, -1].get_width(), color="blue", lw=1)
ax.axhline(y=tbl[1, -1].get_bbox().ymax, color="red", lw=1)
ax.axis("off")

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还可以控制地物和轴的尺寸：

import pandas as pd
import numpy as np
import matplotlib.pyplot as plt

df = pd.DataFrame(np.random.randn(8, 4), columns=["A", "B", "C", "D"])

# Set dimensions
fig, ax = plt.subplots(figsize=df.shape)
ax.axis([0, df.shape[1], df.shape[0], -1]) # xmin, xmax, ymin, ymax

tbl = ax.table(
    cellText=df.values,
    rowLabels=df.index,
    colLabels=df.columns,
    cellLoc="center",
    # loc="center",  # <- don't let matplotlib handle the position
    bbox=(0, 0, 1, 1),  # <- Force the bounding box
    fontsize=20,
    edges="open",
)

ax.axvline(x=0, color="blue", lw=1)
ax.axhline(y=0, color="red", lw=1)
ax.axis('off')
plt.show()

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输出量：

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