python强制结束线程的那点事

　　在使用python3下载图片时，常用的方法有urlretrieve和requests两种，不管哪种方法在网速极慢的情况下，会出现图片下载卡住现象。那如何解决呢？小编根据网上提供的资料测试了几种方法。

1、socket：设置默认超时

　　正常下载的情况

#!/usr/bin/env python3
# -*- coding:utf-8 -*-
# __author__:kzg

import datetime
import os
from urllib.request import urlretrieve
# 函数运行计时器
def count_time(func):
    def int_time(*args, **kwargs):
        start_time = datetime.datetime.now()  # 程序开始时间
        func(*args, **kwargs)
        over_time = datetime.datetime.now()   # 程序结束时间
        total_time = (over_time-start_time).total_seconds()
        print("download picture used time %s seconds" % total_time)
    return int_time
# 下载回调函数， 计算下载进度
def callbackinfo(down, block, size):
    '''
    回调函数：
    down：已经下载的数据块
    block：数据块的大小
    size：远程文件的大小
    '''
    per = 100.0 * (down * block) / size
    if per > 100:
        per = 100
    print('%.2f%%' % per)
# 图片下载
@count_time
def downpic(url, filename):
    try:
        print("Start Down %s" % url)
        if os.path.exists(filename):
            os.remove(filename)
        urlretrieve(url, filename, callbackinfo)
    except socket.timeout as ex:
        print(ex)

url = "http://p1.meituan.net/wedding/d4c375416ab70b8b0bc4247875c929b0434138.jpg%40800w_600h_0e_1l%7Cwatermark%3D1%26%26r%3D1%26p%3D9%26x%3D2%26y%3D2%26relative%3D1%26o%3D20"
filename = r'C:\blueprint-face-detection\scripts\mv.jpg'


downpic(url, filename)


结果：
Start Down http://p1.meituan.net/wedding/d4c375416ab70b8b0bc4247875c929b0434138.jpg%40800w_600h_0e_1l%7Cwatermark%3D1%26%26r%3D1%26p%3D9%26x%3D2%26y%3D2%26relative%3D1%26o%3D20
0.00%
7.01%
14.02%
21.03%
28.04%
35.05%
42.06%
49.07%
56.08%
63.09%
70.10%
77.11%
84.12%
91.13%
98.14%
100.00%
download picture used time 0.165558 seconds

结论：网速较快时下载完全没问题，仅用零点几秒。

2、使用charles限制网速, 设置为下载1k/s, 上传10k/s

　　1、设置charles

　　2、设置socket的默认超时时间为10秒

#!/usr/bin/env python3# -*- coding:utf-8 -*-# __author__:kzgimport datetimeimport osimport socketfrom urllib.request import urlretrieve# 函数运行计时器def count_time(func):    def int_time(*args, **kwargs):        start_time = datetime.datetime.now()  # 程序开始时间        func(*args, **kwargs)        over_time = datetime.datetime.now()   # 程序结束时间        total_time = (over_time-start_time).total_seconds()        print("download picture used time %s seconds" % total_time)    return int_time# 下载回调函数， 计算下载进度def callbackinfo(down, block, size):    '''    回调函数：    down：已经下载的数据块    block：数据块的大小    size：远程文件的大小    '''    per = 100.0 * (down * block) / size    if per > 100:        per = 100    print('%.2f%%' % per)# 图片下载@count_timedef downpic(url, filename):    try:        print("Start Down %s" % url)        if os.path.exists(filename):            os.remove(filename)        urlretrieve(url, filename, callbackinfo)    except socket.timeout as ex:        print(ex)url = "http://p1.meituan.net/wedding/d4c375416ab70b8b0bc4247875c929b0434138.jpg%40800w_600h_0e_1l%7Cwatermark%3D1%26%26r%3D1%26p%3D9%26x%3D2%26y%3D2%26relative%3D1%26o%3D20"filename = r'C:\blueprint-face-detection\scripts\mv.jpg'# 设置10秒超时socket.setdefaulttimeout(10)downpic(url, filename)



结果：
Start Down http://p1.meituan.net/wedding/d4c375416ab70b8b0bc4247875c929b0434138.jpg%40800w_600h_0e_1l%7Cwatermark%3D1%26%26r%3D1%26p%3D9%26x%3D2%26y%3D2%26relative%3D1%26o%3D20
timed out
download picture used time 10.013625 seconds

　　结论：正如期望的那样， 10秒种后下载自动结束了，重试了3次，每次都好使，好高兴 ^_^

猜想，那我把网速提高一些呢，应该更好使吧！！！，下载10k/s, 上传10k/s。