Spent 2 hours debugging CSV import. Turns out Excel added invisible characters.

Spent 2 hours debugging CSV import. Turns out Excel added invisible characters. Client sent me a CSV file yesterday. Simple product list with prices. Import it into my Python script and half the rows fail validation. Opened the CSV in a text editor. Everything looks fine. Columns are there. Data looks clean. Run the script again. Same errors. What broke My script was parsing product prices like this: import csv with open ( ' products.csv ' , ' r ' ) as f : reader = csv . DictReader ( f ) for row in reader : try : price = float ( row [ ' Price ' ]) print ( f " { row [ ' Product ' ] } : $ { price } " ) except ValueError : print ( f " Failed: { row [ ' Product ' ] } - Bad price: ' { row [ ' Price ' ] } '" ) Output showed weird stuff: Product A: $19.99 Failed: Product B - Bad price: '29.99' Product C: $39.99 Failed: Product D - Bad price: '49.99' The prices that failed looked identical to the ones that worked. Copy pasted them into the Python REPL. Worked fine there. Fun. Figured it out ev