if authors and translators:
author_str = ', '.join(authors)
translator_str = '(tłum. ' + ', '.join(translators) + ')'
# just print
parts = [author_str, translator_str]
if authors and translators:
author_str = ', '.join(authors)
translator_str = '(tłum. ' + ', '.join(translators) + ')'
# just print
parts = [author_str, translator_str]