Python code to animate a rotating fan to appear in place

Question

I need to print out rotating fan based on this answer with Python.

import threading
import subprocess

I = 0

class RepeatingTimer(threading._Timer):
    def run(self):
        while True:
            self.finished.wait(self.interval)
            if self.finished.is_set():
                return
            else:
                self.function(*self.args, **self.kwargs)


def status():
    global I
    icons = ['|','/','--','\\']
    print icons[I]
    I += 1
    if I == 4: I = 0

timer = RepeatingTimer(1.0, status)
timer.daemon = True # Allows program to exit if only the thread is alive
timer.start()

proc = subprocess.Popen([ 'python', "wait.py" ])
proc.wait()

timer.cancel()

This code works as I can show the fan, but with carriage return to show as follows.

|
/
--
\
|
/
--
...

What's the python code to print the characters without moving the caret position?

Possible duplicate of http://stackoverflow.com/questions/3249524/print-in-one-line-dynamically-python — yan, Mar 25 '11 at 19:53
@juxstapose : Yes, that's correct. I'll update the question. — prosseek, Mar 25 '11 at 20:07

zarkdav · Accepted Answer · 2011-03-25T22:45:58.777

\n (new line) is automatically inserted by your print statement. The way to avoid it is to end your statement with a comma.

If you want your fan to be on a line on it's own, use:

print icons[I]+"\r",

\r represents the carriage return.

If you want your fan to be at the end of a non-empty line, use \b for the backspace character:

print icons[I]+"\b",

but be wary of not writing anything other than the fan characters after it.

Since print has got some other peculiarities, you may want to go with kshahar suggestion of using sys.stdout.write().

score 3 · Answer 2 · answered Mar 25 '11 at 20:20

3

Here is your total solution:

import itertools
import sys
import time

def whirl(max=50):
    parts = ['|', '/', '-', '\\']

    cnt = 1
    for part in itertools.cycle(parts):
        if cnt >= max:
            break
        sys.stdout.write(part)
        sys.stdout.flush()
        time.sleep(.1)
        sys.stdout.write('\b')
        cnt += 1

answered Mar 25 '11 at 20:20

jathanism

33,067
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1

+1 for showing me `itertools.cycle` I wonder if I'll ever stop finding hidden gems in itertools. – Stephen Paulger Mar 25 '11 at 23:16

nmichaels · Answer 3 · 2011-03-25T20:00:16.717

1

def spin():
    sys.stdout.write('\\')
    sys.stdout.fflush()
    time.sleep(1)
    sys.stdout.write('\b|')

That's a start. print prints newlines; sys.stdout.write doesn't. The \b character is a backspace, and fflush is sometimes necessary to flush buffers when printing incomplete lines. You should be able to extend this method to work with your code pretty easily.

edited Mar 25 '11 at 20:00

answered Mar 25 '11 at 19:53

nmichaels

49,466
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score 0 · Answer 4 · answered Mar 25 '11 at 19:53

0

You could use sys.stdout.write to print without the new lines

sys.stdout.write(icons[I])

answered Mar 25 '11 at 19:53

kshahar

10,423
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missing the flush...stdout.flush() – eat_a_lemon Mar 25 '11 at 19:57

Python code to animate a rotating fan to appear in place

4 Answers4