Working with the Windows Registry

[Larry Bates]

teh_sAbEr wrote:
> Hi everybody. I'm trying to write a script that'll change desktop
> wallpaper every time its run. Heres what I've gotten so far:
> 
> #random wallpaper changer!
> import _winreg
> from os import walk
> from os.path import exists
> from random import randint
> 
> #first grab a registry handle.
> handle = _winreg.OpenKey(_winreg.HKEY_CURRENT_USER,'Control Panel
> \Desktop',_winreg.KEY_SET_VALUE)
> 
> def GenerateListOfWallpapers():
>     targetDir = 'C:\Documents and Settings\Enrico Jr\My Documents\Jr
> \'s Wallpapers'
>     fileNames = []
>     filePaths = []
>     if exists(targetDir):
>         #proceed to make the list of files
>         for x,y,z in walk(targetDir):
>             for name in z:
>                 fileNames.append(name)
>         for item in fileNames:
>             filePaths.append(targetDir + '\\' + item)
>         return filePaths
> 
> def RandomlySelectWallpaper(filePaths):
>     index = randint(0,len(filePaths)-1)
>     RandomlySelectedWallpaper = filePaths[index]
>     return RandomlySelectedWallpaper #it should be a string...
> 
> #now to edit the wallpaper registry key
> newWallpaper = RandomlySelectWallpaper(GenerateListOfWallpapers())
> print "Registry Handle Created."
> print "Random wallpaper selected."
> _winreg.SetValueEx(handle,'ConvertedWallpaper',
> 0,_winreg.REG_SZ,newWallpaper)
> print "New wallpaper value set."
> 
> The problem is, every time I run it, I get an "Access Denied" error
> when it tries to execute
> _winreg.SetValueEx(), even though i've opened the key with the
> KEY_SET_VALUE mask like it said in the help docs. Could there be
> another problem or a better way to do this?

Common error.  You have to open the key so that it can be written as follows:

reg = _winreg.HKEY_CURRENT_USER
key = r'Control Panel\Desktop'
handle = _winreg.OpenKey(reg, key, 0, _winreg.KEY_WRITE)


Note: be careful with backslashes (\) in non-raw strings they will be 
interpreted as escaped sequences.  You were lucky because \D doesn't
represent anything escaped.  You should either use r's\gg\gg' or use double 
backslashes 's\\gg\\gg'.

-Larry