[Jah-yee]

Summary

In the Data Visualisation chapter's exercises section, the example code uses which in Python's plotnine would attempt to reference a variable named rather than the column named .

Changed:

• →

Files changed:

Affected lines (706, 709):

• Exercise 2 code blocks now correctly use with the string column name, matching how the rest of the chapter uses quoted column names.

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This is a single-commit PR with a minimal, surgical fix per the project guidelines.

[Jah-yee]

Hi! This PR fixes the missing quotes around species in the aes() calls in the exercise code. In Python's plotnine, column names must be quoted strings. Happy to make any adjustments!

[Jah-yee]

Update (2026-10-22): I found a bug in my own commit — the added quotes inside the notebook JSON string were unescaped, which makes data-visualise.ipynb fail to parse (JSONDecodeError at line 706). I've amended the commit to escape them as \"species\" so the notebook stays valid JSON while the rendered code still shows aes(x = "species"). The fix is now live on the fix/species-quote-typo branch (commit 91e9ec0). Let me know if you'd like me to adjust anything else!

[Jah-yee]

Hi aeturrell — checking back on the aes() quoting fix in the python4DS exercise notebooks.

The change adds the missing quotes around the species column name in the aes() mappings, which plotnine needs in order to treat it as a variable rather than a literal string. It is confined to the exercise code cells in the notebooks, so no library code is affected.

I also want to flag that my own follow-up commit earlier in this PR fixed an escaping mistake in the notebook JSON string (the added quotes had to be escaped inside the .ipynb source), so the diff you see now includes that correction as well. If the exercise files are regenerated from another source, or if there is a different quoting convention used in the rest of the notebooks, please say so and I will rework it to match.