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LogRedirect.py

import os
import sys
import threading

class LogRedirect:
    def __init__(self, fd=1, dest=sys.stderr, encoding="utf-8", errors="strict"):
        # Save original handle so we can restore it later.
        self.saved_handle = os.dup(fd)
        self.saved_fd = fd
        self.saved_dest = dest

        # Redirect `fd` to the write end of the pipe.
        pipe_read, pipe_write = os.pipe()
        os.dup2(pipe_write, fd)
        os.close(pipe_write)

        # This thread reads from the read end of the pipe.
        def consumer_thread(f, data):
            while True:
                buf = os.read(f, 1024)
                if not buf:
                    break
                data.write(buf.decode(encoding, errors))
            os.close(f)
            return

        # Spawn consumer thread, and give it a mutable `data` item to
        # store the redirected output.
        self.thread = threading.Thread(target=consumer_thread, args=(pipe_read, dest))
        self.thread.start()

    def finish(self):
        # Cleanup: flush streams, restore `fd`
        self.saved_dest.flush()
        os.dup2(self.saved_handle, self.saved_fd)
        os.close(self.saved_handle)
        self.thread.join()