Extracteur INSEE — Ville de Lyon

What I did

• Extraction by area. Import from the census files — both individuals and dwellings — filtered by IRIS, town or canton code, walking the file line by line rather than loading it into memory.
• Composite areas. Extraction by EPCI or by Lyon district, cross-referencing INSEE's geographic-membership tables to resolve the towns and cantons involved.
• Variable decoding. A dictionary built in a single pass over the variable table, keyed by variable code plus modality code, then substituted column by column.
• The format traps. Two dedicated functions: one converts the UTF-8 labels, unreadable as-is in Excel; the other strips leading zeros from modality codes, without which the dictionary keys never match.
• The documentation. A manual covering every procedure, the workbook structure and the common errors — the tool had to stay usable by the department after I left.

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