Getting inspiration from the accepted answer, here's a useful class I wrote, printing a loader à la nodejs cli:

from itertools import cycle
from shutil import get_terminal_size
from threading import Thread
from time import sleep


class Loader:
    def __init__(self, desc="Loading...", end="Done!", timeout=0.1):
        """
        A loader-like context manager

        Args:
            desc (str, optional): The loader's description. Defaults to "Loading...".
            end (str, optional): Final print. Defaults to "Done!".
            timeout (float, optional): Sleep time between prints. Defaults to 0.1.
        """
        self.desc = desc
        self.end = end
        self.timeout = timeout

        self._thread = Thread(target=self._animate, daemon=True)
        self.steps = ["⢿", "⣻", "⣽", "⣾", "⣷", "⣯", "⣟", "⡿"]
        self.done = False

    def start(self):
        self._thread.start()
        return self

    def _animate(self):
        for c in cycle(self.steps):
            if self.done:
                break
            print(f"\r{self.desc} {c}", flush=True, end="")
            sleep(self.timeout)

    def __enter__(self):
        self.start()

    def stop(self):
        self.done = True
        cols = get_terminal_size((80, 20)).columns
        print("\r" + " " * cols, end="", flush=True)
        print(f"\r{self.end}", flush=True)

    def __exit__(self, exc_type, exc_value, tb):
        # handle exceptions with those variables ^
        self.stop()


if __name__ == "__main__":
    with Loader("Loading with context manager..."):
        for i in range(10):
            sleep(0.25)

    loader = Loader("Loading with object...", "That was fast!", 0.05).start()
    for i in range(10):
        sleep(0.25)
    loader.stop()

Also if you're willing to use an external library you might want to look into rich's console.status

from time import sleep
from rich.console import Console

console = Console()
tasks = [f"task {n}" for n in range(1, 11)]

with console.status("[bold green]Working on tasks...") as status:
    while tasks:
        task = tasks.pop(0)
        sleep(1)
        console.log(f"{task} complete")

Just another pretty variant

import time

bar = [
    " [=     ]",
    " [ =    ]",
    " [  =   ]",
    " [   =  ]",
    " [    = ]",
    " [     =]",
    " [    = ]",
    " [   =  ]",
    " [  =   ]",
    " [ =    ]",
]
i = 0

while True:
    print(bar[i % len(bar)], end="\r")
    time.sleep(.2)
    i += 1

Notes:

• Don't use global variables without a good (an extremely good) justification. A function is (should be) a black box that gets values and returns values (unless you have unavoidable side-effects to perform, for example reading a file or printing to the screen).
• It's very cumbersome and inflexible to write every possible string of the progressbar by hand, use code instead to build them.

I'd write:

import sys
import time

def render(size, position):
    return "[" + (" " * position) + "=" + (" " * (size - position - 1)) + "]" 

def draw(size, iterations, channel=sys.stdout, waittime=0.2): 
    for index in range(iterations):
        n = index % (size*2)
        position = (n if n < size else size*2 - n - 1)
        bar = render(size, position)
        channel.write(bar + '\r')
        channel.flush()
        time.sleep(waittime)  

if __name__ == '__main__':
    draw(6, 100, channel=sys.stdout)