Start Phase 9 with pandas

[RamonRDR]

Summary

• start Phase 9: External Libraries with Chapter 01, Working with Tabular Data Using pandas, in English, Brazilian Portuguese, and Spanish
• target the current pandas 3.0.x behavior, researched against the official pandas 3.0.5 documentation
• introduce an explicit third-party dependency contract in requirements-external.txt with pandas>=3.0,<3.1
• update repository CI so approved external-library examples install declared dependencies before execution
• cover Series, DataFrame, indexes, label alignment, dtypes, .loc, .iloc, boolean masks, vectorized assignments, missing-data policy, conversions, string/datetime accessors, grouping, validated joins, reshaping, and CSV pipelines
• document pandas 3.0 version-sensitive behavior, including the dedicated string dtype and Copy-on-Write as the required model, with chained assignment explicitly rejected as an update strategy
• add five deterministic executable pandas examples for table construction, safe conditional assignment, grouped summaries, validated merges, and CSV pipelines
• synchronize repository status, learning paths, roadmaps, project-structure documentation, Phase 9 indexes, and Standard Library → pandas navigation
• mark Phase 9 as in progress, with openpyxl, requests, and pytest planned next

Chapter shape

• 65 numbered sections per language
• 52 fenced Python blocks, identical across EN / PT-BR / ES
• estimated study time: 240–330 minutes
• five new executable examples:
  • dataframe_basics.py
  • filter_and_assign.py
  • groupby_summary.py
  • merge_tables.py
  • csv_pipeline.py

Dependency contract

• requirements-external.txt: pandas>=3.0,<3.1
• pandas 3.0 supports Python 3.11+
• repository CI continues to validate on Python 3.13
• approved external-library examples remain deterministic, non-interactive, and network-free

Validation

• branch is based exactly on main at 5689fb3e70f126ef7c38efc71d64e71b8fdbf8f3
• final clean HEAD: 2f7294bcb9d582e1c5385ef0d865638cb0c0fc38
• one focused commit, 29 changed files
• CPython 3.13.15
• pandas 3.0.5
• all 52 fenced Python blocks are identical across EN / PT-BR / ES
• all three chapters contain exactly 65 numbered sections
• all 11 repository quality-script tests passed
• all 161 approved Python examples passed
• exact output of all five pandas examples passed
• 2,181 internal links across 225 Markdown files passed
• repository structure validation passed
• git diff --check passed
• temporary synchronization script and validation workflow were removed before the clean final commit

References

Primary references are the current official pandas 3.0.5 documentation, User Guide, Getting Started tutorials, Copy-on-Write guide, and pandas 3.0.0 release notes. Version-sensitive behavior is documented explicitly rather than inferred from older pandas 1.x/2.x material.

[RamonRDR]

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[RamonRDR]

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Codex Review: Didn't find any major issues. What shall we delve into next?

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