How to reposition Matplotlib y-axis offset text in stacked subplots: render first, then annotate

Fix overlapping Matplotlib y-axis offset text in stacked subplots: force a draw, use get_offset_text, add an axes fraction annotation, and hide original label.

Stacking multiple subplots in matplotlib often looks straightforward until the y-axis offset text (the scientific-notation exponent) lands right in the middle of the plot above. When the figure uses shared x-axes and compact spacing, the default placement of this offset can overlap with data. Simply calling set_position on the offset text may appear to do nothing, which is confusing when you need the label tucked below the spine.

Minimal example that reproduces the problem

from matplotlib import pyplot as plt
from numpy import linspace, sqrt, pi

fig, axes = plt.subplots(3, 1, sharex=True)
plt.subplots_adjust(hspace=0)


def zr_len(w_zero, lam):
    return pi * w_zero**2 / lam


def waist_zero(lam, L_len, R_len):
    return sqrt(lam / pi * sqrt(L_len * (R_len - L_len)))


def beam_w(z_pos, lam):
    return waist_zero(lam, 0.55, 1) * sqrt(1 + (z_pos / zr_len(waist_zero(lam, 0.55, 1), lam))**2)

x_vals = linspace(0, 1, 5)
y_vals = beam_w(x_vals, 5.54e-6)

for idx in range(3):
    axes[idx].set_xlabel("z / m")
    axes[idx].set_ylabel("$d(w)$ / mm")
    axes[idx].ticklabel_format(axis='y', style='sci', scilimits=(0, 0))
    axes[idx].grid("both", linestyle=":")

    # Attempt to reposition the offset exponent
    axes[idx].get_yaxis().get_offset_text().set_position((0, 0.7))

axes[1].errorbar(x_vals, y_vals, xerr=0.025, yerr=0.2*1e-3, color="black", linestyle="")

plt.show()

What is actually happening

The offset text is empty until the canvas is drawn, which makes it look like repositioning has no effect. After drawing, the text content and its coordinates change. Interactively, the difference looks like this:

>>> axes[2].get_yaxis().get_offset_text()
Text(0, 0.7, '')
>>> fig.canvas.draw()
>>> axes[1].get_yaxis().get_offset_text()
Text(0, 303.3666666666667, '1e−3')

In other words, before rendering, there’s no exponent string to move, and after rendering, matplotlib repositions the label. That explains why a direct set_position call appears ineffective.

Environment details from the discussion show different behavior across versions: the issue was observed with matplotlib 3.9.4 on Arch Linux, while another user on 3.8.4 reported that adjusting coordinates via set_position moved the text. The workaround below does not rely on that and works by replacing the offset with a fixed annotation.

Practical fix: render first, then replace the offset with an annotation

Forcing a draw ensures the exponent is computed. You can then capture the text, place it where you want in axes-relative coordinates, and hide the original offset text so it won’t overlap.

from matplotlib import pyplot as plt
from numpy import linspace, sqrt, pi

fig, axes = plt.subplots(3, 1, sharex=True)
plt.subplots_adjust(hspace=0)


def zr_len(w_zero, lam):
    return pi * w_zero**2 / lam


def waist_zero(lam, L_len, R_len):
    return sqrt(lam / pi * sqrt(L_len * (R_len - L_len)))


def beam_w(z_pos, lam):
    return waist_zero(lam, 0.55, 1) * sqrt(1 + (z_pos / zr_len(waist_zero(lam, 0.55, 1), lam))**2)

x_vals = linspace(0, 1, 5)
y_vals = beam_w(x_vals, 5.54e-6)

for idx in range(3):
    axes[idx].set_xlabel("z / m")
    axes[idx].set_ylabel("$d(w)$ / mm")
    axes[idx].ticklabel_format(axis='y', style='sci', scilimits=(0, 0))
    axes[idx].grid("both", linestyle=":")

axes[1].errorbar(x_vals, y_vals, xerr=0.025, yerr=0.2*1e-3, color="black", linestyle="")

# Force the canvas to compute and place the offset text
fig.canvas.draw()

# Replace the offset text with a custom annotation positioned inside the axes
for idx in range(3):
    y_off = axes[idx].get_yaxis().get_offset_text()
    axes[idx].annotate(y_off.get_text(), xy=(0.01, 0.85), xycoords='axes fraction')
    y_off.set_visible(False)

plt.show()

Why this matters

In stacked plots, label placement directly affects readability. Scientific notation exponents are easy to miss when they collide with plotted data or neighboring axes, and any misread scale can invalidate analysis at a glance. Explicitly controlling the exponent’s placement is a small change with a disproportionate payoff in clarity.

Takeaways

If repositioning the y-axis offset label appears to be ignored, check it after forcing a render. Once the canvas is drawn, the exponent exists and can be replaced with an annotation in axes fraction coordinates, then the original can be hidden. This avoids overlaps in shared-axis layouts and keeps the magnitude indicator visible where it belongs.