Track 15 · Lesson 3 of 11

Combining exports

Merge many CSV exports into one file, even when their columns arrive in different orders and spellings, and remove duplicate records.

You will be able to

• Read every CSV export in a folder in a predictable order and tag each row with its source file
• Use csv.DictReader so that column order does not matter
• Normalise header spellings such as "Order ID" and "order_id" to one form
• Write a combined file with a fixed column order using csv.DictWriter
• Remove duplicate records by key while keeping the first occurrence