stdout2str.py

import os
from contextlib import redirect_stdout

def stdout2str(lambda_func):
    read_fd, write_fd = os.pipe()
    with os.fdopen(write_fd, "w") as write_pipe:
        with redirect_stdout(write_pipe):
            lambda_func()
    with os.fdopen(read_fd, "r") as read_pipe:
        return read_pipe.read()