Spinner in terminal

terminalspinner.py

# coding: utf-8

import sys
import time
import threading
import Queue
import contextlib


ANIMATION = '|/-\\'


class TerminalSpinner(threading.Thread):
    def __init__(self):
        super(TerminalSpinner, self).__init__()
        self.exit_requested = False
        self.message_que = Queue.Queue()
        self.animation = ANIMATION
        self._spin_count = 0
        self._showing_spinner = ''

    def _hide_spinner(self):
        w = len(self._showing_spinner)
        e = '\b' * w + ' ' * w + '\b' * w
        sys.stderr.write(e)
        self._showing_spinner = ''

    def _show_spinner(self, increment=False):
        if increment:
            self._spin_count += 1
            self._spin_count %= len(self.animation)
        self._showing_spinner = self.animation[self._spin_count]
        sys.stderr.write(self._showing_spinner)

    def _flush_queued_messages(self):
        buf = []
        try:
            while True:
                m = self.message_que.get_nowait()
                buf.append(m)
        except Queue.Empty:
            pass
        if buf:
            sys.stderr.write(''.join(buf))

    def run(self):
        self._flush_queued_messages()
        self._show_spinner()
        try:
            while not self.exit_requested:
                time.sleep(0.1)
                self._hide_spinner()
                self._flush_queued_messages()
                self._show_spinner(True)
        finally:
            self._hide_spinner()
            self._flush_queued_messages()


    def write(self, message):
        self.message_que.put(message)
        if self.exit_requested:
            self._flush_queued_messages()

    def join(self):
        self.exit_requested = True
        super(TerminalSpinner, self).join()


@contextlib.contextmanager
def terminal_spinner():
    s = TerminalSpinner()
    s.start()
    try:
        yield s
    finally:
        s.join()


if __name__ == '__main__':
    s = TerminalSpinner()
    s.animation = '(^_^),( ^_),(  ^),(   ),(^  ),(_^ )'.split(',')
    s.write("> doing 1st task ")
    s.start()
    time.sleep(1)
    s.write("then 2nd task ")
    time.sleep(1)
    s.join()
    s.write("... done.\n")

    with terminal_spinner() as a:
        a.write("> another spinner starts")
        time.sleep(1)
        a.write("\n> and messages are shown")
        time.sleep(1)
        a.write("\n> like this.\n")


# Author: Toshihioro Kamiya
# License: Public Domain
# Programming Language: Pyhon 2