how to catch external output to logger

logstdstream.py

log_file = open('example.log', 'a')
logging.basicConfig(stream=log_file, level=logging.DEBUG)
logging.debug("Test")
sys.stdout = log_file
sys.stderr = log_file
stdout_fd = os.dup(1)
stderr_fd = os.dup(2)
os.dup2(log_file.fileno(), 1)
os.dup2(log_file.fileno(), 2)

os.system("echo foo")

os.dup2(stdout_fd, 1)
os.dup2(stderr_fd, 2)
sys.stdout = sys.__stdout__
sys.stderr = sys.__stderr__