majiayu000 Pandas
Pandas is the Excel of Python. v3.0 (2025/2026) enforces Copy-on-Write (CoW), finally fixing the SettingWithCopyWarning confusion.
When to Use
- Data Cleaning: Loading CSV/Excel/SQL and cleaning it.
- Time Series: Unmatched datetime indexing capabilities.
- Small/Medium Data: Features that fit in RAM.
Core Concepts
DataFrame / Series
2D tables and 1D arrays.
Copy-on-Write (CoW)
Views are always views, copies are always copies. Modifying a view triggers a copy only if necessary.
PyArrow Backend
Using Arrow memory format for speed and string handling (dtype="string[pyarrow]").
Best Practices (2025)
Do:
- Use PyArrow Strings:
pd.options.future.infer_string = True(Default in 3.0). - Use
.query(): For cleaner filtering syntax. - Migrate to CoW: Ensure your code doesn't rely on side-effects of views.
Don't:
- Don't iterate rows: Use vectorization (
df['a'] + df['b']).