Python 请求开始从检查点下载文件

Question

我想下载一个带有 Python 请求库的文件。问题是，当我失去与网络的连接时，必须重新下载文件。问题是:我怎样才能让程序知道他最后完成的位置并从这一点开始下载文件？

下面粘贴代码

res = requests.get(link)
playfile = open(file_name, 'wb')

for chunk in res.iter_content(100000):
    playfile.write(chunk)

Answer 1

可以通过 Range 从检查点继续下载。其实你的问题类似于How to `pause`, and `resume` download work? .

这是一个展示其工作原理的示例。

import requests

def DownloadFile(url):
    local_filename = url.split('/')[-1]
    with requests.Session() as s:
        r = s.get(url,headers={"Range": "bytes=0-999"})
        with open(local_filename, 'wb') as fd:
            fd.write(r.content)

        r2 = s.get(url,headers={"Range": "bytes=1000-"})
        with open(local_filename, 'ab') as fd:
            fd.write(r2.content)
    return 
url = "https://upload.wikimedia.org/wikipedia/commons/thumb/6/63/BBC_Radio_logo.svg/210px-BBC_Radio_logo.svg.png" 
DownloadFile(url)

现在，我们可以构建一个从检查点开始下载文件的函数。

import requests
import os

def Continue_(url):
    local_filename = url.split('/')[-1]
    with requests.Session() as s:
        if os.path.exists(local_filename):
            position = os.stat(local_filename).st_size
        else:
            position = 0
        r2 = s.get(url,headers={"Range": "bytes={}-".format(position)})
        with open(local_filename, 'ab+') as fd:
            for c in r2.iter_content():
                fd.write(c)

url = "https://upload.wikimedia.org/wikipedia/commons/thumb/6/63/BBC_Radio_logo.svg/210px-BBC_Radio_logo.svg.png" 

def DownloadFile(url):
    local_filename = url.split('/')[-1]
    with requests.Session() as s:
        r = s.get(url,headers={"Range": "bytes=0-999"})
        with open(local_filename, 'wb') as fd:
            fd.write(r.content)

DownloadFile(url)
Continue_(url)