Python可以用来做什么？公司里主要是爬取数据，并把爬回来的数据进行分析和挖掘，然而我们自己可以用它来爬取一些资源去使用，比如，想看的剧。本文中，小编将分享爬取视频的代码，大家存起来试试吧！
下载流式文件，requests库中请求的stream设为True就可以啦，文档在此。
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：
# -*- coding: utf-8 -*- 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()
加了重复下载的判断，至于怎么源源不断的生产url，诸位摸索吧，保重身体！
【推荐课程：Python视频教程】
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