spinner.py

import sys
import threading
import itertools
import time

# https://stackoverflow.com/questions/4995733/how-to-create-a-spinning-command-line-cursor


class Spinner:
    def __init__(self, message="", delay=0.1):
        self.spinner = itertools.cycle(["-", "/", "|", "\\"])
        self.delay = delay
        self.busy = False
        self.spinner_visible = False
        sys.stdout.write(message)

    def write_next(self):
        with self._screen_lock:
            if not self.spinner_visible:
                sys.stdout.write(next(self.spinner))
                self.spinner_visible = True
                sys.stdout.flush()

    def remove_spinner(self, cleanup=False):
        with self._screen_lock:
            if self.spinner_visible:
                sys.stdout.write("\b")
                self.spinner_visible = False
                if cleanup:
                    sys.stdout.write(" ")  # overwrite spinner with blank
                    sys.stdout.write("\r")  # move to next line
                sys.stdout.flush()

    def spinner_task(self):
        while self.busy:
            self.write_next()
            time.sleep(self.delay)
            self.remove_spinner()

    def __enter__(self):
        if sys.stdout.isatty():
            self._screen_lock = threading.Lock()
            self.busy = True
            self.thread = threading.Thread(target=self.spinner_task)
            self.thread.start()

    def __exit__(self, exception, value, tb):
        if sys.stdout.isatty():
            self.busy = False
            self.remove_spinner(cleanup=True)
        else:
            sys.stdout.write("\r")