标签：python 下载器 多进程

因为爬虫要用到下载器，但是直接用urllib下载很慢，所以找了很久终于找到一个让我欣喜的下载器。他能够断点续传分片下载，极大提高下载速度。

#! /usr/bin/env python

# encoding=utf-8

from __future__ import unicode_literals

from multiprocessing.dummy import Pool as ThreadPool

import threading

import os

import sys

import cPickle

from collections import namedtuple

import urllib2

from urlparse import urlsplit

import time

# global lock

lock = threading.Lock()

# default parameters

defaults = dict(

thread_count=10,

buffer_size=500 * 1024,

block_size=1000 * 1024)

def progress(percent, width=50):

print "%s %d%%\r" % (('%%-%ds' % width) % (width * percent / 100 * '='), percent),

if percent >= 100:

print

sys.stdout.flush()

def write_data(filepath, data):

with open(filepath, 'wb') as output:

cPickle.dump(data, output)

def read_data(filepath):

with open(filepath, 'rb') as output:

return cPickle.load(output)

FileInfo = namedtuple('FileInfo', 'url name size lastmodified')

def get_file_info(url):

class HeadRequest(urllib2.Request):

def get_method(self):

return "HEAD"

res = urllib2.urlopen(HeadRequest(url))

res.read()

headers = dict(res.headers)

size = int(headers.get('content-length', 0))

lastmodified = headers.get('last-modified', '')

name = None

if headers.has_key('content-disposition'):

name = headers['content-disposition'].split('filename=')[1]

if name[0] == '"' or name[0] == "'":

name = name[1:-1]

else:

name = os.path.basename(urlsplit(url)[2])

return FileInfo(url, name, size, lastmodified)

def download(url, output,

thread_count=defaults['thread_count'],

buffer_size=defaults['buffer_size'],

block_size=defaults['block_size']):

# get latest file info

file_info = get_file_info(url)

# init path

if output is None:

output = file_info.name

workpath = '%s.ing' % output

infopath = '%s.inf' % output

# split file to blocks. every block is a array [start, offset, end],

# then each greenlet download filepart according to a block, and

# update the block' offset.

blocks = []

if os.path.exists(infopath):

# load blocks

_x, blocks = read_data(infopath)

if (_x.url != url or

_x.name != file_info.name or

_x.lastmodified != file_info.lastmodified):

blocks = []

if len(blocks) == 0:

# set blocks

if block_size > file_info.size:

blocks = [[0, 0, file_info.size]]

else:

block_count, remain = divmod(file_info.size, block_size)

blocks = [[i * block_size, i * block_size,

(i + 1) * block_size - 1] for i in range(block_count)]

blocks[-1][-1] += remain

# create new blank workpath

with open(workpath, 'wb') as fobj:

fobj.write('')

print 'Downloading %s' % url

# start monitor

threading.Thread(target=_monitor, args=(

infopath, file_info, blocks)).start()

# start downloading

with open(workpath, 'rb+') as fobj:

args = [(url, blocks[i], fobj, buffer_size)

for i in range(len(blocks)) if blocks[i][1] < blocks[i][2]]

if thread_count > len(args):

thread_count = len(args)

pool = ThreadPool(thread_count)

pool.map(_worker, args)

pool.close()

pool.join()

# rename workpath to output

if os.path.exists(output):

os.remove(output)

os.rename(workpath, output)

# delete infopath

if os.path.exists(infopath):

os.remove(infopath)

assert all([block[1] >= block[2] for block in blocks]) is True

def _worker((url, block, fobj, buffer_size)):

req = urllib2.Request(url)

req.headers['Range'] = 'bytes=%s-%s' % (block[1], block[2])

res = urllib2.urlopen(req)

while 1:

chunk = res.read(buffer_size)

if not chunk:

break

with lock:

fobj.seek(block[1])

fobj.write(chunk)

block[1] += len(chunk)

def _monitor(infopath, file_info, blocks):

while 1:

with lock:

percent = sum([block[1] - block[0]

for block in blocks]) * 100 / file_info.size

progress(percent)

if percent >= 100:

break

write_data(infopath, (file_info, blocks))

time.sleep(2)

if __name__ == '__main__':

import argparse

parser = argparse.ArgumentParser(description='多线程文件下载器.')

parser.add_argument('url', type=str, help='下载连接')

parser.add_argument('-o', type=str, default=None,

dest="output", help='输出文件')

parser.add_argument(

'-t', type=int, default=defaults['thread_count'], dest="thread_count", help='下载的线程数量')

parser.add_argument(

'-b', type=int, default=defaults['buffer_size'], dest="buffer_size", help='缓存大小')

parser.add_argument(

'-s', type=int, default=defaults['block_size'], dest="block_size", help='字区大小')

argv = sys.argv[1:]

if len(argv) == 0:

argv = ['https://eyes.nasa.gov/eyesproduct/EYES/os/win']

args = parser.parse_args(argv)

start_time = time.time()

download(args.url, args.output, args.thread_count,

args.buffer_size, args.block_size)

print '下载时间: %ds' % int(time.time() - start_time)