automatic proxy detect on windows

[zhangn1985]

On Linux maybe Mac, we can use os.getenv('http_proxy') to detect system proxy.

But on Windows, things different.

basically via register:

try:
    import winreg as registry
except:
    import _winreg as registry

key=registry.OpenKey(registry.HKEY_CURRENT_USER,"Software\Microsoft\Windows\CurrentVersion\Internet Settings\Connections",0,registry.KEY_ALL_ACCESS)
(value, regtype) = registry.QueryValueEx(key, "DefaultConnectionSettings")
print(value)

but value are binary format, I don't know how to parse it. help is needed.

[zhangn1985]

class urllib.request.ProxyHandler(proxies=None)

Cause requests to go through a proxy. If proxies is given, it must be a dictionary mapping protocol names to URLs of proxies. The default is to read the list of proxies from the environment variables _proxy. If no proxy environment variables are set, then in a Windows environment proxy settings are obtained from the registry’s Internet Settings section, and in a Mac OS X environment proxy information is retrieved from the OS X System Configuration Framework.

[zhangn1985]

we need to add a hint to tell code, we use system proxy.