python gtk loop ascii spinner

问题:

I am trying (for testing) to have a little ascii spinner object being printed on the screen during a gtk.main() loop. Currently, I have this code which prints a dot every two seconds.

    gobject.timeout_add(2 * 1000,
            lambda : (sys.stdout.write('.'), sys.stdout.flush()) )
    gtk.main()

However, I would like the traditional ascii spinner instead but cannot get a good lambda for it. Any suggestions?

Edit: Two good answers but is there a way to do this with a lambda? Just 'cause lambda are cool. Nothing more.

回答1:

Why are you limiting yourself to a lambda? To do a spinner, it's easiest to maintain state:

class Spinner(object):
  def __init__(self):
    self._chars = r"-\|/-\|/"
    self._pos = 0

  def spin(self):
    sys.stdout.write(self._chars[self._pos])
    sys.stdout.write("\r")
    sys.stdout.flush()
    self._pos += 1
    if self._pos >= len(self._chars):
      self._pos = 0
    return True

spinner = Spinner()
gobject.timeout_add(2 * 1000, spinner.spin)

Note: the above is untested, but should make the general idea clear enough.

回答2:

This is something I've just tried in the console without gtk:

import sys
from itertools import cycle
from time import sleep

spinner = r'-\|/'

sys.stdout.write('Please wait... ')

for character in cycle(spinner):
    sys.stdout.write(character)
    sys.stdout.flush()
    sys.stdout.write('\b')
    sleep(1)

The two things I like that are slightly different from the previous solution are:

• Use \b instead of \r to preserve any message you have in the same line (like "please wait")
• cicle takes care of what's the next character for you, so you don't need to bother to manage the state yourself.