新技能 get —— Python 断点续传下载文件

from urllib.request import urlretrieve
import sys
import os

prev_reported_download_percent = None

# 首先定义下载 hook，作为 urllib.request.urlretrive 的关键字参数
def download_hook(count, block_size, total_size):
    """ 接口是写死的 """
    global prev_reported_download_percent
    percent = int(count*block_size*100/total_size)
    if prev_reported_download_percent != percent:
        if percent % 5 == 0:
            sys.stdout.write('%s%%' % percent)
            sys.stdout.flush()
        else:
            sys.stdout.write('.')
            sys.stdout.flush()
        prev_reported_download_percent = percent

def maybe_download(filename, force=False):
    """ force 表示是否强制下载 """
    if force or not os.path.exists(filename):
        print('Attempting to download')
        filename, _ = urlretrieve(url+filename, filename, reporthook=download_hook)
            # url+filename：表示文件的 url 地址，
            # filename 则为保存到本地时的文件名
        print('\nDownload completed!')
    # statinfo = os.stat(filename)
    return filename

比如对于 http://ufldl.stanford.edu/housenumbers/ 网站下的 train.tar.gz/test.tar.gz两文件，客户端的调用方式为：

url = 'http://ufldl.stanford.edu/housenumbers/'
train_filename = maybe_download('train.tar.gz')
test_filename = maybe_download('test.tar.gz')