import re
splited_file = open(output_path, 'w', encoding = 'utf-8')
with open("файл.txt") as f:
articles = re.split(r'\n\s*\n', f.read(), flags=re.M)
for i in range(len(articles)):
article = articles[i]
file_name = "{}{}.txt".format(article[:20],str(i))
file = open(file_name, mode='w')
file.write(article)
file.close()