Please see for the code:

• cpython/Modules/_csv.c

  Lines 1253 to 1267 in 7dc42b6

  	if (!field_len && dialect->delimiter == ' ' && dialect->skipinitialspace) {
  	if (dialect->quoting == QUOTE_NONE ||
  	(field == NULL &&
  	(dialect->quoting == QUOTE_STRINGS ||
  	dialect->quoting == QUOTE_NOTNULL)))
  	{
  	PyErr_Format(self->error_obj,
  	"empty field must be quoted if delimiter is a space "
  	"and skipinitialspace is true");
  	return 0;
  	}
  	quoted = 1;
  	}
  	rec_len = join_append_data(self, field_kind, field_data, field_len,
  	&quoted, 0);

Please see the test:

• https://github.com/python/cpython/pull/115721/files#diff-dd5e5efc1566b1c1dc988769a04cc403d2416c8af5bf4785bec235d02a780813R352-R354

The behavior is intentional since gh-115721, so the only sensible route is to update the docs.

• Issue: Document that CSV skipinitialspace=True and delimiter=' ' require quotation for empty fields #138005

📚 Documentation preview 📚: https://cpython-previews--138006.org.readthedocs.build/