Change browser proxy settings from Python?

Question

I have written a program that relies on a proxy to function. I now need a script that will check to see if the browser is set to use the right proxy, and if not, change it t

Answer 1

The Windows stores its system wide proxy in the registry, look in the the HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Internet Settings. You can use the Python _winreg module to change it (or just winreg if you use Python 3). Here is a sample code

import _winreg as winreg

INTERNET_SETTINGS = winreg.OpenKey(winreg.HKEY_CURRENT_USER,
    r'Software\Microsoft\Windows\CurrentVersion\Internet Settings',
    0, winreg.KEY_ALL_ACCESS)

def set_key(name, value):
    _, reg_type = winreg.QueryValueEx(INTERNET_SETTINGS, name)
    winreg.SetValueEx(INTERNET_SETTINGS, name, 0, reg_type, value)

set_key('ProxyEnable', 1)
set_key('ProxyOverride', u'*.local;<local>')  # Bypass the proxy for localhost
set_key('ProxyServer', u'X.X.X.X:8080')

To disable it you can just need to set ProxyEnable key to 0:

set_key('ProxyEnable', 0)

After the script runs the browsers will still have the old proxy stored in-memory, so you need to restart them so they can re-read the new proxy settings from the registry. I found this to be very annoying so I converted this snippet to Python.

import ctypes

INTERNET_OPTION_REFRESH = 37
INTERNET_OPTION_SETTINGS_CHANGED = 39

internet_set_option = ctypes.windll.Wininet.InternetSetOptionW

internet_set_option(0, self.INTERNET_OPTION_REFRESH, 0, 0)
internet_set_option(0, self.INTERNET_OPTION_SETTINGS_CHANGED, 0, 0)

This refreshes the Windows settings so all you have to do is hit F5 in your browser in order to it grab the new proxy settings.

I've written a small script to switch my proxy on or off, the source in on Bitbucket: https://bitbucket.org/canassa/switch-proxy

This should work with any browser that uses the Windows system-wide proxy (e.g.: Chrome, IE). Some browsers like Firefox uses a internal proxy settings. If you want to change these you will have figure out where they store their settings and write code to change it.

Answer 2

Much thanks to @Cesar Canassa, but there is a small problem, you should always refresh after you change the setting, otherwise the changes you just made in winreg will be discarded when you refresh. So it should be like this.

import ctypes

INTERNET_OPTION_REFRESH = 37
INTERNET_OPTION_SETTINGS_CHANGED = 39

internet_set_option = ctypes.windll.Wininet.InternetSetOptionW

internet_set_option(0, INTERNET_OPTION_SETTINGS_CHANGED, 0, 0)
internet_set_option(0, INTERNET_OPTION_REFRESH, 0, 0)