Python how to make simple animated loading while process is running

Use a thread:

import itertools
import threading
import time
import sys

done = False
#here is the animation
def animate():
    for c in itertools.cycle(['|', "https://stackoverflow.com/", '-', '\\']):
        if done:
            break
        sys.stdout.write('\rloading ' + c)
        sys.stdout.flush()
        time.sleep(0.1)
    sys.stdout.write('\rDone!     ')

t = threading.Thread(target=animate)
t.start()

#long process here
time.sleep(10)
done = True

I also made a couple of minor modifications to your animate() function, the only really important one was adding sys.stdout.flush() after the sys.stdout.write() calls.