pyreadstat

.sas7bdat is the binary format SAS uses to store data sets. SAS is commercial statistical software with a licensing cost that prices out most individual users. The format is proprietary and undocumented by SAS, so every reader outside it, including pyreadstat, is the product of reverse engineering.

A single .sas7bdat file holds the table itself, the column metadata, and enough type information to reconstruct rows. What it does not hold is the display layer. SAS stores human-readable value labels and formats in a separate catalog file, .sas7bcat. Converting to CSV throws that layer away, because CSV has no place to put it.