Pedagogy: merge 00_introduction/50_pandas + 20_probability/30_pandas → 06_python_advanced/90_pandas

[kwlee2025cpp]

Goal

Pandas is currently taught in two notebooks:

• 00_introduction/50_pandas.ipynb (~40 cells): Series, DataFrame, vectorization, .shift, .astype, toy data
• 20_probability/30_pandas.ipynb (~180 cells): read_html, dropna, set_index, .loc/.at, .isin, .str, seaborn, real Naver Finance data

The two are sequential (basics → application), not duplicative. But they live in mismatched folders — 20_probability/30_pandas has no probability content — and the split into two files creates a discoverability gap.

Scope

Create 06_python_advanced/90_pandas.ipynb by merging the two:

1. Series and DataFrame fundamentals (from old 00/50)
2. I/O and cleaning — read_csv / read_html, dropna, set_index, dtypes (from old 20/30)
3. Selection and querying — .loc, .at, .isin, .str methods (from old 20/30)
4. Visualization — quick seaborn intro (from old 20/30)
5. Vectorization vs loops — concluding hook (from old 00/50)

Trim duplicated Series/DataFrame intro cells so each concept appears once.

Retire 00_introduction/50_pandas.ipynb and 20_probability/30_pandas.ipynb after the merge lands.

Why

• One canonical pandas notebook, in the right folder.
• 20_probability/ stops claiming to teach pandas (it never did).
• Aligns with the broader 00_introduction restructure (libraries move to 06_).

Acceptance

• 06_python_advanced/90_pandas.ipynb exists and runs end-to-end.
• No content lost from either source notebook (each concept appears at least once).
• Both old notebooks removed (or stub-redirected for one CI cycle, then removed).