如何在Matplotlib中同时实现等比例坐标轴与紧凑布局？

我想要在等比例坐标轴上绘制一组多边形，并对图形应用tight layout。但同时使用等比例（equal aspect）和tight layout时，图形尺寸似乎无法正确调整。

尝试1：启用等比例与紧凑布局 #

启用等比例与紧凑布局后，图形上下存在多余空白，且y轴标签超出边界。

import matplotlib.pyplot as plt
from matplotlib.patches import Polygon
import numpy as np

fig, ax = plt.subplots(1,1)
l = 5
h = 1
poly = Polygon(
    np.array([
        [0,0],
        [l,0],
        [l,h],
        [0,h]
    ]),
    edgecolor="black",
    facecolor="gray",
)
ax.add_patch(poly)
ax.set_aspect("equal")
ax.set_xlim(0,l)
ax.set_ylim(0,h)
ax.set_xlabel(r"$x$")
ax.set_ylabel(r"$y$", rotation=0, labelpad=5)
fig.tight_layout(pad=0.25)
plt.show()

尝试2：仅启用紧凑布局（关闭等比例） #

布局正常，但坐标轴比例不等。

import matplotlib.pyplot as plt
from matplotlib.patches import Polygon
import numpy as np

fig, ax = plt.subplots(1,1)
l = 5
h = 1
poly = Polygon(
    np.array([
        [0,0],
        [l,0],
        [l,h],
        [0,h]
    ]),
    edgecolor="black",
    facecolor="gray",
)
ax.add_patch(poly)
# ax.set_aspect("equal")
ax.set_xlim(0,l)
ax.set_ylim(0,h)
ax.set_xlabel(r"$x$")
ax.set_ylabel(r"$y$", rotation=0, labelpad=5)
fig.tight_layout(pad=0.25)
plt.show()

请问如何同时实现tight layout与等比例坐标轴？

方法1：使用constrained_layout替代tight_layout #

constrained_layout是Matplotlib更先进的布局机制，能更好适配固定坐标轴比例的场景，动态调整元素位置避免标签截断或多余空白。

import matplotlib.pyplot as plt
from matplotlib.patches import Polygon
import numpy as np

# 创建画布时启用constrained_layout
fig, ax = plt.subplots(1, 1, constrained_layout=True)
l = 5
h = 1
poly = Polygon(
    np.array([
        [0,0],
        [l,0],
        [l,h],
        [0,h]
    ]),
    edgecolor="black",
    facecolor="gray",
)
ax.add_patch(poly)
ax.set_aspect("equal")
ax.set_xlim(0, l)
ax.set_ylim(0, h)
ax.set_xlabel(r"$x$")
ax.set_ylabel(r"$y$", rotation=0, labelpad=5)
plt.show()

方法2：手动设置画布尺寸适配坐标轴比例 #

根据坐标轴的实际范围比例，手动指定画布figsize，让轴的尺寸与比例匹配后再应用tight_layout。

比如x轴范围0-5，y轴0-1，比例为5:1，可设置画布宽高比为5:1：

import matplotlib.pyplot as plt
from matplotlib.patches import Polygon
import numpy as np

# 按坐标轴比例设置figsize，这里宽8，高8*(1/5)=1.6
fig, ax = plt.subplots(1, 1, figsize=(8, 1.6))
l = 5
h = 1
poly = Polygon(
    np.array([
        [0,0],
        [l,0],
        [l,h],
        [0,h]
    ]),
    edgecolor="black",
    facecolor="gray",
)
ax.add_patch(poly)
ax.set_aspect("equal")
ax.set_xlim(0, l)
ax.set_ylim(0, h)
ax.set_xlabel(r"$x$")
ax.set_ylabel(r"$y$", rotation=0, labelpad=5)
fig.tight_layout(pad=0.25)
plt.show()

方法3：先布局再应用坐标轴比例 #

先执行tight_layout调整元素位置，再设置等比例并强制应用布局更新：

import matplotlib.pyplot as plt
from matplotlib.patches import Polygon
import numpy as np

fig, ax = plt.subplots(1, 1)
l = 5
h = 1
poly = Polygon(
    np.array([
        [0,0],
        [l,0],
        [l,h],
        [0,h]
    ]),
    edgecolor="black",
    facecolor="gray",
)
ax.add_patch(poly)
ax.set_xlim(0, l)
ax.set_ylim(0, h)
ax.set_xlabel(r"$x$")
ax.set_ylabel(r"$y$", rotation=0, labelpad=5)

# 先完成紧凑布局
fig.tight_layout(pad=0.25)
# 设置等比例并强制应用
ax.set_aspect("equal")
ax.apply_aspect()
plt.show()

内容的提问来源于stack exchange，提问作者Zxcvasdf