Script downloading file from filesonic

Could somebody please advise me on how I could write a Python script to do these things?

1. Change my IP address to some random proxy address.
2. Download and display the captcha image and show me the prompt where I can write captcha characters.
3. Download the main file.

The script should have one input parameter (the address is similar to one of these):

http://www.filesonic.com/file/212720521/Ubuntu.11.04.part1.rar

http://www.filesonic.com/file/212720541/Ubuntu.11.04.part2.rar

It would be called开发者_如何学JAVA twice as follows:

python dlsonic.py http://www.filesonic.com/file/212720521/Ubuntu.11.04.part1.rar
python dlsonic.py http://www.filesonic.com/file/212720541/Ubuntu.11.04.part2.rar

Here's some basic Python to get you started:

import urllib2
response = urllib2.urlopen('http://www.example.com/')
html = response.read() # This is what is read from the file. In your case,
                       # it'll only read the contents of the webpage.

To change your IP address, you can use some Linux commands to accomplish this (assuming you're using ethernet here):

ifconfig eth0 192.168.1.5 netmask 255.255.255.0 up
ifconfig eth0

And with Python, you can run these with os.system():

import os
os.system('ifconfig eth0 192.168.1.5 netmask 255.255.255.0 up')
os.system('ifconfig eth0')

And to handle command line arguments, like python foo.py bar foo bar bar:

import sys
print sys.argv

As for dealing with the CAPTCHA, that will be tough. Are you sure you can't just do this manually?