题
我正在从网络服务器下载整个目录。它工作正常,但我不知道如何在下载之前获取文件大小以比较它是否在服务器上更新。这可以像我从 FTP 服务器下载文件一样完成吗?
import urllib
import re
url = "http://www.someurl.com"
# Download the page locally
f = urllib.urlopen(url)
html = f.read()
f.close()
f = open ("temp.htm", "w")
f.write (html)
f.close()
# List only the .TXT / .ZIP files
fnames = re.findall('^.*<a href="(\w+(?:\.txt|.zip)?)".*$', html, re.MULTILINE)
for fname in fnames:
print fname, "..."
f = urllib.urlopen(url + "/" + fname)
#### Here I want to check the filesize to download or not ####
file = f.read()
f.close()
f = open (fname, "w")
f.write (file)
f.close()
@乔恩:感谢您的快速答复。它可以工作,但 Web 服务器上的文件大小略小于下载文件的文件大小。
例子:
Local Size Server Size
2.223.533 2.115.516
664.603 662.121
和 CR/LF 转换有什么关系吗?
解决方案
我已经重现了您所看到的内容:
import urllib, os
link = "http://python.org"
print "opening url:", link
site = urllib.urlopen(link)
meta = site.info()
print "Content-Length:", meta.getheaders("Content-Length")[0]
f = open("out.txt", "r")
print "File on disk:",len(f.read())
f.close()
f = open("out.txt", "w")
f.write(site.read())
site.close()
f.close()
f = open("out.txt", "r")
print "File on disk after download:",len(f.read())
f.close()
print "os.stat().st_size returns:", os.stat("out.txt").st_size
输出这个:
opening url: http://python.org
Content-Length: 16535
File on disk: 16535
File on disk after download: 16535
os.stat().st_size returns: 16861
我在这里做错了什么?os.stat().st_size 是否未返回正确的大小?
编辑:好的,我知道问题出在哪里了:
import urllib, os
link = "http://python.org"
print "opening url:", link
site = urllib.urlopen(link)
meta = site.info()
print "Content-Length:", meta.getheaders("Content-Length")[0]
f = open("out.txt", "rb")
print "File on disk:",len(f.read())
f.close()
f = open("out.txt", "wb")
f.write(site.read())
site.close()
f.close()
f = open("out.txt", "rb")
print "File on disk after download:",len(f.read())
f.close()
print "os.stat().st_size returns:", os.stat("out.txt").st_size
这输出:
$ python test.py
opening url: http://python.org
Content-Length: 16535
File on disk: 16535
File on disk after download: 16535
os.stat().st_size returns: 16535
确保打开两个文件以进行二进制读/写。
// open for binary write
open(filename, "wb")
// open for binary read
open(filename, "rb")
其他提示
使用 returned-urllib-object 方法 info()
, ,您可以获取有关检索到的文档的各种信息。抓取当前Google徽标的示例:
>>> import urllib
>>> d = urllib.urlopen("http://www.google.co.uk/logos/olympics08_opening.gif")
>>> print d.info()
Content-Type: image/gif
Last-Modified: Thu, 07 Aug 2008 16:20:19 GMT
Expires: Sun, 17 Jan 2038 19:14:07 GMT
Cache-Control: public
Date: Fri, 08 Aug 2008 13:40:41 GMT
Server: gws
Content-Length: 20172
Connection: Close
这是一个字典,所以要获取文件的大小,你需要这样做 urllibobject.info()['Content-Length']
print f.info()['Content-Length']
要获取本地文件的大小(用于比较),可以使用 os.stat() 命令:
os.stat("/the/local/file.zip").st_size
文件的大小作为 Content-Length 标头发送。下面是如何使用 urllib 获取它:
>>> site = urllib.urlopen("http://python.org")
>>> meta = site.info()
>>> print meta.getheaders("Content-Length")
['16535']
>>>
在Python3中:
>>> import urllib.request
>>> site = urllib.request.urlopen("http://python.org")
>>> print("FileSize: ", site.length)
对于 python3(在 3.5 上测试)方法,我建议:
with urlopen(file_url) as in_file, open(local_file_address, 'wb') as out_file:
print(in_file.getheader('Content-Length'))
out_file.write(response.read())
A 要求使用 HEAD 而不是 GET 的基于解决方案(还打印 HTTP 标头):
#!/usr/bin/python
# display size of a remote file without downloading
from __future__ import print_function
import sys
import requests
# number of bytes in a megabyte
MBFACTOR = float(1 << 20)
response = requests.head(sys.argv[1], allow_redirects=True)
print("\n".join([('{:<40}: {}'.format(k, v)) for k, v in response.headers.items()]))
size = response.headers.get('content-length', 0)
print('{:<40}: {:.2f} MB'.format('FILE SIZE', int(size) / MBFACTOR))
用法
$ python filesize-remote-url.py https://httpbin.org/image/jpeg ... Content-Length : 35588 FILE SIZE (MB) : 0.03 MB
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