代码描述:
当你创建用户界面并想保持界面的可用性时,线程就特别有用。
没有线程,用户界面将变得迟钝,当你下载一个大文件或者执
行一个庞大的数据库查询命令时用户界面会长时间无响应。为
了防止这样情况发生,你可以使用多线程来处理运行时间长的
进程并且在完成后返回界面进行交互。
import threading
from urllib.request import urlopen
DOWNLOAD_DIR = 'doc'
class DownloadThread(threading.Thread):
def __init__(self, url):
super(DownloadThread, self).__init__()
self.url = url
def run(self):
try:
urlObj = urlopen(self.url, timeout=3)
except Exception as e:
print("download %s error\n" % (self.url), e)
imgContent = None
else:
# http://imgsrc.baidu.com/forum/w%3D580/sign=16d420cb8b01a18bf0eb1247ae2e0761/22a4462309f790520522e1d900f3d7ca7bcbd51c.jpg
filename = self.url.split("/")[-1]
# 'wb' === 写的是二进制文件(图片, 视频, 动图, .pdf)
# 'ab'
with open("%s/%s" % (DOWNLOAD_DIR, filename), 'ab') as f:
# 如果文件特别大的时候, 建议分块下载;每次只读取固定大小, 防止占用内存过大.
while True:
imgContentChunk = urlObj.read(1024 * 3)
if not imgContentChunk:
break
f.write(imgContentChunk)
# 可以添加下载的程度(百分率);
print("%s下载成功" % (filename))
url1 = "ftp://172.25.254.250/pub/book/python/01_MIT.Introduction.to.Computation.and.Programming.Using.Python%20revised%20and%20expanded%20edition.pdf"
# url2 = "ftp://172.25.254.250/pub/book/python/01_python%E6%A0%B8%E5%BF%83%E7%BC%96%E7%A8%8B.pdf"
# url3 = "ftp://172.25.254.250/pub/book/python/02_Python%20Cookbook%EF%BC%88%E7%AC%AC3%E7%89%88%EF%BC%89%E4%B8%AD%E6%96%87%E7%89%88.pdf"
url2 = 'ftp://172.25.254.250/pub/book/python/02_interview_exercise.pdf'
url3 = "ftp://172.25.254.250/pub/book/python/02_python-data-structure-cn.pdf"
urls = [url1, url2, url3]
for url in urls:
thread = DownloadThread(url)
thread.start()