Python tutorial on handling concurrency using period objects

import os
import time
import sys
import requests
POP20_CC = ('CN IN US ID BR PK NG BD RU JP ' 'MX PH VN ET EG DE IR TR CD FR').split()
BASE_URL = '/data/flags'
DEST_DIR = './'
def save_flag(img, filename):  # Save images
    path = (DEST_DIR, filename)
    with open(path, 'wb') as fp:
        (img)
def get_flag(cc):  # Get the image
    url = '{}/{cc}/{cc}.gif'.format(BASE_URL, cc=())
    resp = (url)
    return 
def show(text):  # Print information
    print(text, end=' ')
    ()
def download_many(cc_list):
    for cc in sorted(cc_list):
        image = get_flag(cc)  # Get
        show(cc)  # Print
        save_flag(image, () + '.gif')  # Save
    return len(cc_list)
def main(download_many):
    t0 = ()
    count = download_many(POP20_CC)
    elapsed = () - t0
    msg = '\n{} flags downloaded in {:.2f}s'
    print((count, elapsed))  # Timing information
# ---- Implementing multithreaded downloads using classes
from concurrent import futures
MAX_WORKERS = 20  # Maximum number of threads used
def download_one(cc):
    image = get_flag(cc)
    show(cc)
    save_flag(image, () + '.gif')
    return cc
def download_many_1(cc_list):
    workers = min(MAX_WORKERS, len(cc_list))
    with (workers) as executor:
        # Instantiate the ThreadPoolExecutor class with the number of threads working;
        # executor.__exit__ method calls the (wait=True) method.
        # It'll block the thread until all the threads have finished #
        res = (download_one, sorted(cc_list))
        The # download_one function is called concurrently in multiple threads;
        # The map method returns a generator, so you can iterate over it and get the values returned by each function.
    return len(list(res))
if __name__ == '__main__':
    # main(download_many) # 24 seconds
    main(download_many_1)  # 3 unit of angle or arc equivalent one sixtieth of a degree

def download_many_2(cc_list):
    cc_list = cc_list[:5]
    with (max_workers=3) as executor:
        to_do = []
        for cc in sorted(cc_list):
            future = (download_one, cc)
            # method schedules the execution time of the callable object.
            # and then returns an object indicating the pending operation.
            to_do.append(future) # Stored issues
            msg = 'Scheduled for {}: {}'
            print((cc, future))
        results = []
        for future in futures.as_completed(to_do):
            # as_completed function outputs an issue at the end of an issue run
            res = () # Results of acquisitions
            msg = '{} result: {!r}'
            print((future, res))
            (res)
    return len(results)

exports：
Scheduled for BR: <Future at 0x22da99d2d30 state=running>
Scheduled for CN: <Future at 0x22da99e1040 state=running>
Scheduled for ID: <Future at 0x22da99e1b20 state=running>
Scheduled for IN: <Future at 0x22da99ec520 state=pending>
Scheduled for US: <Future at 0x22da99ecd00 state=pending>
CN <Future at 0x22da99e1040 state=finished returned str> result: 'CN'
BR <Future at 0x22da99d2d30 state=finished returned str> result: 'BR'
ID <Future at 0x22da99e1b20 state=finished returned str> result: 'ID'
IN <Future at 0x22da99ec520 state=finished returned str> result: 'IN'
US <Future at 0x22da99ecd00 state=finished returned str> result: 'US'
5 flags downloaded in 3.20s