Write the JSON Document

The converter now holds ordinary Python values with the right meaning. The json module’s job is to serialize them: turn the in-memory object into JSON text with the required escaping and punctuation.

Build the envelope first

The list of items belongs under the exact top-level schema:

document = {
    "schema_version": 1,
    "items": items,
}

That Python dictionary is the document’s logical shape. Serialization is a separate operation. Do not assemble JSON with f-strings or str(document): Python spells booleans True and False, while JSON requires true and false; quoting and escaping have more cases than one example reveals.

dump writes to a file

json.dump(value, handle, ...) serializes directly into an open text file:

with open(path, "w", encoding="utf-8") as handle:
    json.dump(document, handle, ensure_ascii=False, indent=2, allow_nan=False)
    handle.write("\n")

• ensure_ascii=False keeps Café readable in the UTF-8 file.

• indent=2 gives deterministic, reviewable output.

• allow_nan=False refuses non-finite numbers that JSON’s standard does not contain.

• json.dump does not add a final newline, so the file contract adds one.

The s names the string version: json.dumps(document) returns JSON text as a Python string, while json.dump(document, handle) writes to an open file. Both serialize one value. The same pairing works in reverse: load reads an open file and loads parses a string. Lesson 5 uses that reading pair.

Your turn

Implement write_catalog_json(items, path) and convert_catalog(input_path, output_path).

write_catalog_json builds the exact envelope, writes it with the options above, and returns the document it wrote. convert_catalog reads and converts the CSV through read_catalog_csv, passes those items to the writer, and returns the same document.

Run the project after implementing the two functions only if you also call them temporarily yourself; main is still a no-op until Lesson 6. The checks call the functions directly and inspect the actual output file. They also use an unseen CSV, so a hard-coded copy of the seeded JSON cannot pass.