Keeping postal codes as strings in Python fixture round trips

Postal codes can look numeric, but converting them to numbers drops leading zeros that cannot be restored by converting back to text. Codes with letters and spaces, such as Canadian-style formats, also need to be preserved exactly. A tutorial demonstrates an offline Python 3.10+ check using only the standard library to verify a JSON address export against a CSV file with a ZIP column. The check confirms that postal values remain strings, source references are retained, and each CSV row matches its JSON record field by field. The fixtures are invented for testing purposes and are not real postal reference data.