python 网络下载的三种风格 未完成

import os
import time
import sys

import requests
#依序下载
POP20_CC = (‘CN IN US ID BR PK NG BD RU JP‘
            ‘MX PH VN ET EG DE IR TE CD TR‘).split()
BASE_URL = ‘http://flupy.org/data/flags‘
DEST_DIR = ‘downloads/‘


def save_flag(img, filename):
    path = os.path.join(DEST_DIR, filename)
    if not os.path.isdir(DEST_DIR):
        os.mkdir(DEST_DIR)

    with open(path, ‘wb‘) as fp:
        if fp.writable():
            fp.write(img)


def get_flag(cc):#下载内容
    url = ‘{}/{cc}/{cc}.gif‘.format(BASE_URL, cc=cc.lower())  # 格式化字符串{BASE_URL}/{cc}/{cc}
    print(url)
    resp = requests.get(url)#以二进制形式下载
    return resp.content#返回二进制数据


def show(text):
    print(text,end=‘ ‘)
    sys.stdout.flush()#在liunx系统下，不加这句，打印时间不是立刻打印的。假如在windows中不存在这个问题（正常情况遇到换行才会刷新stdout缓冲）

def download_many(cc_list):
    for cc in sorted(cc_list):#sorted()这个排序的结果和作用是什么？
        image=get_flag(cc)
        show(cc)

        save_flag(image,cc.lower()+‘.gif‘)
    return len(cc_list)

def main_n(download_many):
    t1=time.time()
    count=download_many(POP20_CC)
    elapsed=time.time()-t1
    msg=‘\n{} flags download in {:.2f}s‘
    print(msg.format(count,elapsed))

if __name__ == ‘__main__‘:
    main_n(download_many)
#BD BR CD CN DE EG ET ID IN IR JPMX NG PH PK RU TE TR US VN
# 19 flags download in 8.57s






#concurrent.futures 模块下载

from concurrent import futures
import os
import time
import requests
import sys

MAX_WORKERS = 20
POP20_CC = (‘CN IN US ID BR PK NG BD RU JP‘
            ‘MX PH VN ET EG DE IR TE CD TR‘).split()
BASE_URL = ‘http://flupy.org/data/flags‘
DEST_DIR = ‘downloads/‘


def save_flag(img, filename):
    path = os.path.join(DEST_DIR, filename)
    if not os.path.isdir(DEST_DIR):
        os.mkdir(DEST_DIR)

    with open(path, ‘wb‘) as fp:
        if fp.writable():
            fp.write(img)


def get_flag(cc):
    url = ‘{}/{cc}/{cc}.gif‘.format(BASE_URL, cc=cc.lower())
    resp = requests.get(url)
    return resp.content


def show(text):
    print(text, end=‘ ‘)
    sys.stdout.flush()


def main_n(download_many):
    t1 = time.time()
    count = download_many(POP20_CC)
    elapsed = time.time() - t1
    msg = ‘\n{} flags download in {:.2f}s‘
    print(msg.format(count, elapsed))


def download_one(cc):
    image = get_flag(cc)
    show(cc)
    save_flag(image, cc.lower() + ‘.gif‘)
    return cc


def download_many(cc_list):
    workers = min(MAX_WORKERS, len(cc_list))  # 设置最大线程数

    with futures.ThreadPoolExecutor(workers) as executor:
        res = executor.map(download_one, sorted(cc_list))
    return len(list(res))


# BD BR CN ID EG JPMX IN NG RU TE ET CD IR PH PK VN DE US TR
# 19 flags download in 2.44s
if __name__ == ‘__main__‘:
    main_n(download_many)

python 网络下载的三种风格 未完成

原文：https://www.cnblogs.com/yanxiatingyu/p/9326244.html