先找一个视频地址试验一下：

# -*- coding: utf-8 -*-

import requests

def download_file(url, path):

with requests.get(url, stream=True) as r:

chunk_size = 1024

content_size = int(r.headers['content-length'])

print '下载开始'

with open(path, "wb") as f:

for chunk in r.iter_content(chunk_size=chunk_size):

f.write(chunk)

if __name__ == '__main__':

url = '就在原帖...'

path = '想存哪都行'

download_file(url, path)

遭遇当头一棒：

AttributeError: __exit__

这文档也会骗人的么！

看样子是没有实现上下文需要的__exit__方法。既然只是为了保证要让r最后close以释放连接池，那就使用contextlib的closing特性好了：

# -*- coding: utf-8 -*-

import requests

from contextlib import closing

def download_file(url, path):

with closing(requests.get(url, stream=True)) as r:

chunk_size = 1024

content_size = int(r.headers['content-length'])

print '下载开始'

with open(path, "wb") as f:

for chunk in r.iter_content(chunk_size=chunk_size):

f.write(chunk)

程序正常运行了，不过我盯着这文件，怎么大小不见变啊，到底是完成了多少了呢？还是要让下好的内容及时存进硬盘，还能省点内存是不是：

# -*- coding: utf-8 -*-

import requests

from contextlib import closing

import os

def download_file(url, path):

with closing(requests.get(url, stream=True)) as r:

chunk_size = 1024

content_size = int(r.headers['content-length'])

print '下载开始'

with open(path, "wb") as f:

for chunk in r.iter_content(chunk_size=chunk_size):

f.write(chunk)

f.flush()

os.fsync(f.fileno())

文件以肉眼可见的速度在增大，真心疼我的硬盘，还是最后一次写入硬盘吧，程序中记个数就好了：

def download_file(url, path):

with closing(requests.get(url, stream=True)) as r:

chunk_size = 1024

content_size = int(r.headers['content-length'])

print '下载开始'

with open(path, "wb") as f:

n = 1

for chunk in r.iter_content(chunk_size=chunk_size):

loaded = n*1024.0/content_size

f.write(chunk)

print '已下载{0:%}'.format(loaded)

n += 1

结果就很直观了：

已下载2.579129%

已下载2.581255%

已下载2.583382%

已下载2.585508%

心怀远大理想的我怎么会只满足于这一个呢，写个类一起使用吧：

# -*- coding: utf-8 -*-

import requests

from contextlib import closing

import time

def download_file(url, path):

with closing(requests.get(url, stream=True)) as r:

chunk_size = 1024*10

content_size = int(r.headers['content-length'])

print '下载开始'

with open(path, "wb") as f:

p = ProgressData(size = content_size, unit='Kb', block=chunk_size)

for chunk in r.iter_content(chunk_size=chunk_size):

f.write(chunk)

p.output()

class ProgressData(object):

def __init__(self, block,size, unit, file_name='', ):

self.file_name = file_name

self.block = block/1000.0

self.size = size/1000.0

self.unit = unit

self.count = 0

self.start = time.time()

def output(self):

self.end = time.time()

self.count += 1

speed = self.block/(self.end-self.start) if (self.end-self.start)>0 else 0

self.start = time.time()

loaded = self.count*self.block

progress = round(loaded/self.size, 4)

if loaded >= self.size:

print u'%s下载完成\r\n'%self.file_name

else:

print u'{0}下载进度{1:.2f}{2}/{3:.2f}{4} 下载速度{5:.2%} {6:.2f}{7}/s'.\

format(self.file_name, loaded, self.unit,\

self.size, self.unit, progress, speed, self.unit)

print '%50s'%('/'*int((1-progress)*50))

运行：

下载开始

下载进度10.24Kb/120174.05Kb 0.01% 下载速度4.75Kb/s

/

下载进度20.48Kb/120174.05Kb 0.02% 下载速度32.93Kb/s

/

看上去舒服多了。

下面要做的就是多线程同时下载了，主线程生产url放入队列，下载线程获取url：

import requests

from contextlib import closing

import time

import Queue

import hashlib

import threading

import os

def download_file(url, path):

with closing(requests.get(url, stream=True)) as r:

chunk_size = 1024*10

content_size = int(r.headers['content-length'])

if os.path.exists(path) and os.path.getsize(path)>=content_size:

print '已下载'

return

print '下载开始'

with open(path, "wb") as f:

p = ProgressData(size = content_size, unit='Kb', block=chunk_size, file_name=path)

for chunk in r.iter_content(chunk_size=chunk_size):

f.write(chunk)

p.output()

class ProgressData(object):

def __init__(self, block,size, unit, file_name='', ):

self.file_name = file_name

self.block = block/1000.0

self.size = size/1000.0

self.unit = unit

self.count = 0

self.start = time.time()

def output(self):

self.end = time.time()

self.count += 1

speed = self.block/(self.end-self.start) if (self.end-self.start)>0 else 0

self.start = time.time()

loaded = self.count*self.block

progress = round(loaded/self.size, 4)

if loaded >= self.size:

print u'%s下载完成\r\n'%self.file_name

else:

print u'{0}下载进度{1:.2f}{2}/{3:.2f}{4} {5:.2%} 下载速度{6:.2f}{7}/s'.\

format(self.file_name, loaded, self.unit,\

self.size, self.unit, progress, speed, self.unit)

print '%50s'%('/'*int((1-progress)*50))

queue = Queue.Queue()

def run():

while True:

url = queue.get(timeout=100)

if url is None:

print u'全下完啦'

break

h = hashlib.md5()

h.update(url)

name = h.hexdigest()

path = 'e:/download/' + name + '.mp4'

download_file(url, path)

def get_url():

queue.put(None)

if __name__ == '__main__':

get_url()

for i in xrange(4):

t = threading.Thread(target=run)

t.daemon = True

t.start()