import os
import re

path_txt = (r'C:UsersusuarioDesktopfiles')

name_files = os.listdir(path_txt)

for TXT in name_files:
    with open(path_txt + '\' + TXT, "r") as content:
        search = re.search(r'(([0-9]{4})(/)(([1][9][0-9][0-9])|([2][0-9][0-9][0-9])))', content.read())
    if search is not None:
        os.rename(os.path.join(path_txt, TXT),
                  os.path.join("Processos3", search.group(0) + "_" + str(random.randint(100, 999)) + ".txt"))