Silence matplotlib 3.11's font-weight fallback warning in the i18n font cells

[mmcky]

Refs #110. This is the current fix for that issue, which stays open while other approaches are considered.

Problem

Since the anaconda 2026.07 bump (#102), matplotlib 3.11 prints findfont: Failed to find font weight normal, now using 600. in 17 lectures, 77 times in all. It goes to stderr, so it shows on the rendered pages.

The cause is that we ship only the SemiBold weight of Source Han Serif SC, and matplotlib falls back to it for normal and bold text. 3.10 did this silently; 3.11 logs it. Details are in #110.

Change

In the 18 lectures that call fontManager.addfont, add two # i18n lines directly after the existing font registration:

import logging  # i18n
logging.getLogger('matplotlib.font_manager').setLevel(logging.ERROR)  # i18n

The lines follow the existing # i18n convention for zh-cn-only code. No other lines change: 36 insertions in 18 files.

Effect

• The font manager's lookup messages are hidden, which restores the 3.10 behaviour.
• Figures are unchanged. The fallback still uses the SemiBold face, and a PNG drawn with and without the warning is byte-identical.
• Missing glyphs are still reported, because matplotlib raises them through Python's warnings module, not this logger.

Testing

• I extracted the # i18n font setup from each of the 18 lectures and ran it under matplotlib 3.11.0 with a figure containing Chinese normal and bold text. None printed anything.
• This PR's preview build re-executes all 18 lectures under anaconda 2026.07. Their outputs should no longer contain findfont.

🤖 Generated with Claude Code

https://claude.ai/code/session_01Wyb6EzbNzY5a8uuJPnDtUb

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Generated by Claude Code

[Copilot]

🟢 Approval recommended

The change is a mechanical, consistent, and correct logger-level adjustment applied to all 18 lectures that register the font, with no missed files or logic issues.

0 open findings

What changed in this PR

This PR silences the findfont: Failed to find font weight normal, now using 600. warning that matplotlib 3.11 (pulled in by the anaconda 2026.07 bump in #102) emits to stderr and renders onto 17 lecture pages. The repository only ships the SemiBold weight of Source Han Serif SC, so matplotlib falls back to it for normal/bold text; 3.10 did this silently while 3.11 logs it. The fix raises the matplotlib.font_manager logger to ERROR immediately after the existing font registration, restoring the 3.10 output behavior without changing any rendered figures.

Changes:

• Adds import logging # i18n and logging.getLogger('matplotlib.font_manager').setLevel(logging.ERROR) # i18n directly after the fontManager.addfont call in each affected lecture.
• Applies this consistently across all 18 lectures that register the Chinese font, following the existing trailing # i18n convention for zh-cn-only code.

File	Description
lectures/​about_py.md	Adds logger-silencing lines after font registration
lectures/​debugging.md	Adds logger-silencing lines after font registration
lectures/​functions.md	Adds logger-silencing lines after font registration
lectures/​jax_intro.md	Adds logger-silencing lines after font registration
lectures/​matplotlib.md	Adds logger-silencing lines after font registration
lectures/​need_for_speed.md	Adds logger-silencing lines after font registration
lectures/​numba.md	Adds logger-silencing lines after font registration
lectures/​numpy.md	Adds logger-silencing lines after font registration
lectures/​numpy_vs_numba_vs_jax.md	Adds logger-silencing lines after font registration
lectures/​pandas.md	Adds logger-silencing lines after font registration
lectures/​pandas_panel.md	Adds logger-silencing lines after font registration
lectures/​python_advanced_features.md	Adds logger-silencing lines after font registration
lectures/​python_by_example.md	Adds logger-silencing lines after font registration
lectures/​python_oop.md	Adds logger-silencing lines after font registration
lectures/​scipy.md	Adds logger-silencing lines after font registration
lectures/​sympy.md	Adds logger-silencing lines after font registration
lectures/​workspace.md	Adds logger-silencing lines after font registration
lectures/​writing_good_code.md	Adds logger-silencing lines after font registration

🧠 Review effort: Balanced

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