Non-blocking file-like class for read() (Python)

nonblocking.py

import threading

class NonBlocking(threading.Thread):
    def __init__(self, fp):
        threading.Thread.__init__(self)
        self.fp = fp
        self.read_buffer = []
        self.running = True
        self.start()

    def run(self):
        while self.running:
            byte_read = self.fp.read(1)
            self.read_buffer.append(byte_read)
        self.fp.close()

    def read(self, size=None):
        if not len(self.read_buffer):
            value = None
        else:
            if not size:
                size = len(self.read_buffer)
            value = ''.join(self.read_buffer[:size])
            self.read_buffer = self.read_buffer[size:]
        return value

    def readline(self):
        if '\n' in self.read_buffer:
            line_feed_index = self.read_buffer.index('\n')
            value = ''.join(self.read_buffer[:line_feed_index + 1])
            self.read_buffer = self.read_buffer[line_feed_index + 1:]
        else:
            value = None
        return value
    
    def close(self):
        self.running = False